1. Written Exam 
2. Personal Interview

Preliminary Examination

1.Current events of national and international importance.

2.History of India and Indian national movements.

3.Indian and World geography-Physical, Social, Economic Geography of India and the world.

4.Indian polity and governance-Constitution, political system, Panchayati raj, public policy, Rights Issues, etc.

5.Economic and Social development-sustainable development, poverty, inclusion, Demographics, Social Sector initiatives, etc.

6.General issues on Environmental Ecology, Bio-diversity, and climate change that don't require subject specialization.

7.General science

Paper- 2  is the Civil service aptitude test, Popularly known as CSAT Paper. Questions are asked from the following section in this paper.

1.Comprehension.

2.Interpersonal skills including communication skills.

3.Logical reasoning and Analytical ability.

4.Decision making and problem-solving.

5.General mental ability.

6.Basic numeracy(numbers and their relations, orders of magnitude)(Class-X level).

Data interpretation(charts,graphs,tables,data sufficiency etc)(class-x level).

7.English language comprehension skills(class-x level).

1. All you need is to qualify for Paper-2 so that your paper-1 will be evaluated. So huge and extensive practice is not required here. But, Yes, You should not neglect this paper. You just solve the past years' papers so that you will get the idea of the type of questions they are asking. Along with it, you will come to know your weak areas so that you will work more on them to improve.
2.  You may take the help of online coaching[ most preferable nowadays] if you think this paper is creating problems for you.
3. In the exam hall, you will get 2 hours to solve this paper. So for speed and accuracy, you need a little bit of practice otherwise you can not answer many questions for which you know the answers.
4. Returning home, you can answer many of them but in the exam hall, you can not. The reason for it is the lack of practice.
5. From my experience, I am telling you you divide the time into two parts, one hour each. For the first one hour, you solve the aptitude or the math section and in the 2nd  hour, you solve the English passage and other questions.
6. Do not stick to a question whose idea is not coming to your mind. Skip it and go ahead. Time management is the key in the examination hall.
7. At least you should answer 50 questions correctly from your point of view. After deducting the marks for the wrong answers, you will be in a comfortable stage to qualify the paper.
8. Those who are exceptionally good at this paper, no need for them to panic. They should exclusively focus on paper-1.
9. My suggestion is, don't take this paper for granted, devote some time for this paper so that you will be absolutely confident for this paper before the exam.

Paper-1 Preparation Strategy

1. This paper is the most important one in the preliminary Examination.
2. 100 questions are asked in this paper. Each question carries 2 marks. 2 marks are awarded for correct answer and [1/4]th of 2 marks i.e 0.5 marks is deducted for the wrong answer.
3. The marks you secure in this paper will be considered for merit if you will be qualified for the main exam or not.
4.  I have mentioned the seven sections above from which questions are asked in this paper. You can see these are very subjective in nature.
5. my suggestion is, go through the past years' papers of paper-1 and try to find out the type of questions they are asking each year. So that you will get the idea of preparing for this paper.
6. From my experience, I am telling you, this paper is in between  UPSC and SSC types of questions. Most of the questions are factual and data-based. We have to byheart certain things which are mandatory.
7. After analysis of the past papers, you will get to know, questions like the constitutional amendment, Headquarters of international organizations, Reports published by different national and international organizations, Joint Military Exercises, Naval and Airforce Exercises, Awards, Books & Authors, Indexes, Important Days and their themes, National parks, etc. are asked each year. So you should prepare these sections very nicely.
8.  The following article will give you an elaborate compilation of these sections in a very lucid way.  Most Probable Valuable Random Facts For OAS Prelim
9. For History, First Cover the Modern Indian History From the Book Spectrum Modern India.  You can read the Old NCERT's book for Modern Indian History if you have. Read the Book once and underline the important ones. For the second time, you read the underlined ones.  After this refer to Tarun Goyal GK or Kiran's One-liner or Lucent GK. to read the compilation. Either of these books is good for revision.
10. Nowadays 5 to 6 questions are asked from medieval Indian History. Only read the compilation from the books I have mentioned above. If you have time go through the NCERT's books.
11. One or two questions will be asked from Ancient India, so only read the compilation of these books mentioned above.
12. There is no world History in the Preliminary exam, so don't panic.
13. For Geography, NCERT's  Fundamentals of physical Geography & India: Physical Environment, these two books are sufficient. Along with it solve a lot of MCQs from any Objective book. In my opinion, Disha's 10000+ is a good one. 
14. For Indian Polity, M. Laxmikanth is the best book. Read this book multiple times so that you will grasp the basics nicely.
15. Prepare some famous landmark judgments of the supreme court. These are necessary from prelim and main exam points of view. For this, you can read the book " Important Judgements that transformed India" by Alex Andrews George.
16. For Economics, NCERT's A textbook of MacroEconomics is the basic one. You will get many basic pieces of stuff from this book. For other things, you can refer to Ramesh Singh[ No need to read the whole book]
17. You can take the help of Google, Youtube, or your seniors to understand the different concepts of Economics.
18. For Environment & Ecology, Read Chapters 13, 14, 15,16 of Class 12 Biology Book of NCERT.
19. You Can Refer Sankar IAS Environment Book for few advanced things.
20. For General Science, read the compilation from Tarun Goyal GK or Kiran's one-liner or Lucent GK.  Either of these book's compilation for General Science will be sufficient.
21. For Current affairs of national and international importance, make some notes of important points which are generally asked in the Prelim Exam. Current affairs are so vast. You can not read everything. Read some selected and important ones which are absolutely required.
22. For Practice and more clarity of the content, you need to solve a lot of MCQs from any Objective books available. But in my opinion, Disha's 10000+ is a good one.
23. Make habit of reading News Paper Daily. so that you will get yourself updated on different current issues on daily basis, Initially reading News Paper will be boring and time-consuming but once you get acquainted, you will enjoy it.
24. You can read this article for various relevant books and resources for the preparation of the prelim exam. Book list( syllabus wise) for OAS prelim exam 2020
25. Unlike the main exam where questions are predictable, in the prelim, nothing can be predicted. But one thing is for sure, they will definitely ask questions from basics. So revise the basics again and again. You will definitely clear the prelim. Trust me. 

1.  In Main Written Exam, there are two language papers. i.e  Odia Language paper & English Language Paper. You need to qualify for these two papers so that your other paper will be evaluated. Each Paper contains 300 marks. For General category boys, qualifying marks is 35% i.e at least 105 marks out of 300, you have to score to qualify. The qualifying marks are different for different categories of students.
2. In Odia language paper, you analyze the past papers and see how questions are asked. Those who are from CBSE & ICSE, Do writing practice. Focus more on Odia Grammar as these are more scoring.
4. In the English Language paper, focus more on grammar, usages like one-word substitution, synonyms, and antonyms, prepositions, idioms & phrases, voice change, narration change, relative clause, etc. Analyze the past papers so that you will get an idea of the questions asked.
5. There is a paper on English Essay. In this paper, you will be writing a single essay for 200 marks. This Essay paper is very important to get a good rank. At least you have to score 100+ marks on this paper. First thing in the essay, you should read a number of essays of past years' toppers and see how they write their essays.
6. The most important thing in the essay is your representation of the content of the essay. Do not worry. you will get the content from various subjects you read while preparing for the general studies paper.
7. In the exam paper, there will be a number of essays and you have to choose one. The selection of the right essay is the most crucial thing. From my experience, I am telling you, always try to choose the essay which is based on current issues. It is because you will get a lot of examples and content in the essay.
8. The next crucial thing is the structure of the essay. Always try to write a catchy introduction that will reflect a glimpse of the whole essay. There are various ways of starting the essay but starting the essay with a quotation or a short story is a nice approach as I have experienced.
9. While writing the body of the essay, make it multidimensional. Do not write the essay in a single direction. After understanding the content of the essay, Include every possible perspective. to describe the content in a multidimensional way. It will add both your maturity and intellect to your essay.
10. While writing, make heading and sub-headings so that they will be more structured and easy to read.
11. Conclude the essay on a positive note so that the whole essay will be convincing and will meet a logical end. Always choose a middle path while writing your suggestions.
12. The essay is of 100 marks so write the essay in 2000 words.
13. Use simple English and avoid ornamental words while writing.
14. There are two optional subjects in the main written exam. You have to choose two optional subjects out of a number of optional subjects given by OPSC.
15. Choosing the right optional is the key to get success in this exam. My personal experience is, go for Humanities optional subjects. You will get an ample amount of materials for these subjects on the internet and in the market also.
16. OUAT optional subjects like forestry are very good but you should have a biology background for this. Apart from this, you should collect notes from OUAT professors as these professors are going to check the papers. Over the years OUAT optional subjects are doing good. Students are scoring more than 250+ marks in each paper of those optional subjects.
17. Humanities optional subjects like sociology, history, home science, political science & International relation, public administration, geography, psychology, philosophy, etc are doing well over the years. Many students have got success with these optional subjects.  
18. My personal opinion is, Sociology & Home Science is a good combination to score high marks.
19. Click the article to read the strategy for sociology. Sociology tips, chapter wise strategy, best books, and pdfs for OPSC OAS exam
20. Click the article to read the strategy for Home Science. Home science tips, syllabus, and book list for opsc OAS exam
21. In optional Papers, most of the questions are predictable. The only thing you need to do is to do a nice writing practice so that with the prescribed time you can write all the answers perfectly.
22. In each paper of optional subjects, there are 8 questions. 4 questions in section-A and 4 questions in section-B.  Question no-1 in section-A & Question no- 5 in Section-B are compulsory. You have to answer a total of 5 questions out of 8 questions. 2 questions are compulsory [ i.e Q-1 from Section-A & Q-5 from Section-B]. The rest 3 questions are answered either one question from section-A and two questions from Section-B or one question from section-B and two questions from Section-A which one is suitable for you.
23. If you have a good grip on mathematics and are ready to do a lot of practice, go for mathematics optional. It is also scoring. Do a lot of numerical practice otherwise it will be a disaster.
24. Don't go for  Engineering optional subjects and other science optional subjects as the success rate of these optional subjects are negligible.
25. Whatever the optional subjects you are choosing, analyze each topic of the syllabus of that subject looking at the past years' papers. You will come to know the most important and relevant topics from which each year questions are asked. Prepare notes for those topics nicely.
26. You collect notes from various sources and consolidate them for multiple revisions.
27.  Regular revision and writing practice will make you score high on optional papers. Trust me.
28. Each optional paper is of 300 marks and you will be given 3 hrs to answer them. Students are scoring 250+ in each paper of the optional subjects. Scoring 220+ in each optional subject is a nice one to get a good rank.
29. There are two GS papers i.e paper-1 & paper-2. Each paper will of 300 marks and you will be given 3 hrs to answer them.
30. For GS papers, you read the syllabus carefully and analyze the past papers. you will come to know that each and every question are directly from the topics mentioned in the syllabus. Hence, you need to prepare notes for each and every topic mentioned in the syllabus. 
31. Revise those notes time and again. Writing practice is very crucial and an absolute need to do well in GS papers.
32. If you are a serious aspirant, the answer to every question is familiar to you. You know the answer to each and every question. The only challenge is to complete the paper within 3hrs duration. You can not answer all the questions if you do not have sufficient writing practice.
33. For the preparation of notes of various topics of the GS syllabus, You can use the Internet smartly.

Personal Interview

1. After the publication of the main result, you will get approximately 1 month time to prepare for the exam.
2. Your knowledge has already been stated in the prelim and main written exams. Here they want to know the type of persona you are carrying.
3. They will ask questions both in Odia and English language to know your vocal ability and the way you are explaining things.
4. Mostly they will ask questions about your graduation subjects, optional subjects, and current issues. Sometimes they ask questions from your home districts. So prepare accordingly.
5. Most questions are basic in nature. Their only intention is to test your clarity in understanding the basic things. i.e how you explain those things in a very lucid and simple manner.
6. Make yourself formally dressed and be confident on the interview day.
7. Usually, 2 to 3 boards are formed. OPSC chairman and members are the members of these boards. On each board, 3 to 4 members are there. They are very very cordial and helpful. Always they will make you comfortable. Approximately, the interview will continue for 15 to 20 minutes.
8. The interview is conducted for 250 marks.  200+ is a good score. Sometimes people score 240+ and sometimes below 50 also. So you need to prepare well to score around 200 marks which is the standard score.