2) Now buy syllabus of GS and your optional. Go through it comprehensively.
3) Buy previous 10 years question papers of prelims and mains for your optional and GS.
Make sure that these question papers are divided question wise.
4) Now go through the questions to understand the pattern of the paper. After you have seen what the exam expects out of you, start studying the basic books.
5) When you are studying basic books for GS and optional, do not go about making notes and cramming stuff. This first reading is meant to acquaint you with concepts. So focus on conceptual understanding no matter how factual the subject is.
6) Always try to understand the central aspect of any topic and not the peripheral aspects. Peripheral aspects will naturally follow.
7) Do not just start preparing for prelims exclusively. The idea is that you should first prepare holistically for prelims and mains together and towards the last 3 4 months you can focus exclusively on prelims.
8) Always keep sight of the question paper pattern. Do some problem solving for both prelims and mains.
9)Take regular breaks. Noone can keep working non stop. :-)
10) Keep a chart to track your progress. I did that and that helps.
hope this helps.