To become an OAS officer is a dream for every competitive aspirant. You cannot get it as a gift from your parents. You have to strive hard. You should know about the exam structure and syllabus. At first you have to qualify in prelims, then mains and finally the interview. The prelim exam comprises multiple choice type questions. Therefore, you should focus on certain portion. To boost preparation, you should gather ideas from seniors and professional teachers. You have to discuss the topics with your friends to get mastery over them.