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Dear Vedprakash,
Some of the reputed coaching institutes are Career Launcher, Chanakya, RAU's IAS academy etc.
https://www.shiksha.com/search/index?keyword=IAS&location=&searchType=course&cat_id=&countOffsetSearch=25&startOffSetSearch=0&subLocation=-1&cityId=-1&cType=-1&courseLevel=-1&subType=0&showCluster=-1&channelId=
(In the above link, you can refine the search as per your preferred city)
The minimum qualification required for IAS is graduation from a reputed university. There are two stages that you need to clear- preliminary exam and main exam. In order to prepare for IAS the minimum requirement is graduation from a recognized university and the age group is 21-30yrs. For your preparation I would suggest you to first join a good coaching center so that you have the relevant study material to start your preparation.
CSAT: It is an Objective type examination consisting of Two Papers that is common to all candidates from 2011 having special emphasis on testing their aptitude for civil services as well as on general knowledge.
Main Exam.: Those who qualify the CSAT exam are shortlisted for the Main exam. It is a descriptive (essay type) examination. The General Studies, Essay paper, English Paper are common to all candidates and with this a candidate has two optional subjects to choose from the given options and a language paper of his / her choice. Here you can opt for subjects like Maths, Eco, Phy, stats etc.
Hope this helps.
Thanks
All The Best!