I have 4 Year study time for IAS preparation. I have finished my 12th std and joined Agriculture bsc. can you please guide me how to study for IAS?

As you are doing your graduation you'll have to balance both your graduation and your studies for preparation for UPSC. As you have 4 years you can prepare easily even if you give 6 hours a day, not much is  required as you have 4 years. Now how you will give 6 hours a day depends upon you. For example, if your college starts at 9:00 you can wake up at 5 ,get fresh by 5:30 and can study till it 8 , again after 1 hour of returning from college , you can study for 2 hours for UPSC, then again have some break and after which you can study for your college and before you sleep you can again give 2 hours towards your UPSC preparation so that you can give a total of 6 hours in a day. It will a  little difficult to manage at starting but soon you will get used to it, just try to do this for 21 days and you will soo get into your routine :)

Follow the below tips to prepare well for your UPSC  examination :-

To start your preparation  first of all go well through syllabus  , you can check the complete syllabus at
https://competition.careers360.com/articles/upsc-ias-syllabus

Top books which you can follow for UPSC examination preparation are listed below subject wise:-

HISTORY

*NCERT XI (Ancient & Medieval)
*NCERT XII (Modern Indian History)
*Facets of Indian Culture Spectrum
*From Plassey to Partition - A History of Modern India

Indian Art & Culture

*Indian Art & Culture - Nitin Singhania

Polity

*NCERT IX-XII
*Indian Polity M Laxmikanth

Geography

*NCERT VI X (Old Syllabus)
*NCERT XI, XII (New Syllabus)
*Certificate Physical Geography G C Leong
World Atlas

Economics

NCERT XI
*The Indian Economy Sanjiv Verma
*Indian Economy by Ramesh Singh
*Economic Development & Policies in India Jain & Ohri

Environment

*Class XII Biology (last 5 chapters)
*Environment by Shankar IAS Academy

International Relations

*NCERT XII (Contemporary World Politics)
*Current Affairs ( read newspaper )

To get the complete list of books go through
https://competition.careers360.com/articles/books-for-upsc-ias

*Make a routine or a time table and try to religiously follow it , take short breaks in between your studies.

*Read newspaper daily and keep yourself updated with the current affairs

*Choose your optional subject wisely , choose the subject you have interest in.

*Make short notes for each subject, it  will help you in your revisions a lot as syllabus is wide

*Set daily goals like I have to cover these many topics today, weekly goals like I have to  cover these chapters this week and practice their questions too, by the end of this week and similarly set monthly goals to cover the syllabus and meet them without any fail.

*Revise :- there's no point of preparing for the exam if you couldn't recall anything in the UPSC Examination so you should stress on revision as well.

* Your mains examination is in written, so you need to work your speed and also work on improving how to present the knowledge you have on paper, so answer writing practicing should be also your priority

*Solve previous year question papers and mock test papers ;- You should solve these , it will give you idea of types of questions asked and their difficulty level and will help you a lot.

*Also work on your communication skills and personality development as it plays an important role in your interview round

For more tips go through

https://competition.careers360.com/articles/how-prepare-for-upsc-ias

I hope my answer helps. All the very best for your future endeavors!