I have been asked by many aspirants about the right strategy, tips, "how to study", right books so as to qualify UPSC CSE. Since I was already working in a job aspirants already working somewhere come to me with a special hope.
I too like them, had wasted 3-4 years looking for same things. 2 years while in college and 2 years while in job. During this course I met many aspirants preparing with me, read interviews of successful candidates in the hope of discovering something. If I am not wrong, they are also looking for some particular magic, thinking there must be some very special way in which successful aspirants prepare themselves.
Sorry to disappoint you all, but there is no such thing.There is no strategy, no golden list of books, no magic way. UPSC isn't looking for very intelligent, genius candidates. If at all there are some qualities that it is looking for, they could be retention, recall, reproduce.
The only strategy that would help one remember voluminous study materials and reproduce them in a desired way has to be discovered by oneself. The test that a candidate should apply to check whether his strategy is working or not is this: Whenever you have gone through a particular topic think whether you can now write 300 words ( short topics) and 600-800 words ( long topics) on that particular topic.Whether you can relate that topic to other topics in the same chapter and happenings around you. If you cannot do all of this then you have not prepared that topic.
Many aspirants (especially engineers) apply the modus operandi of their college exams to UPSC, study a chapter and then think that since they have an idea about the topic and they already brilliant they would be able to answer any question from that topic. The sooner they realize their folly and correct themselves, better for them.
The right strategy can vary anywhere from going through the same topic again and again ( 3-4 times), reading different sources ( max 3) and making one's own notes or reading others' notes including class notes of coaching classes and adding noting to it or anything else. It depends on the person and his/her ability to mug up. One has to try until one gets it right. My strategy used to going through 2 or 3 sources for a topic and making my own detailed notes for topic like one writes the chapter of a book.
My other successful friends have done it by making bulleted notes for topics after reading it from different sources or by not making any notes at all. For some people note-making leads to reproduction of book matter having no value addition. One might make notes after reading 2 basic books then come back to notes after 2-3 months and find that it was all junk. In that case one may have to rewrite the notes for that topic. This happens since note-making and reading abilities gradually improve with preparation.
One might require a slight retouch to the old notes after going through a better source ( a new book or someone else's notes). This cycle goes on till the day of exam and one need not worry too much about this. It only means one is improving. However more than 2 rewriting s does indicate that a lot of time was wasted.
Those who are already in jobs must remember that there cannot be any special exemption for them. Having a job in hand has a small advantage and a big disadvantage. One does not have to worry about financial aspects and one can free anxiety that surrounds joblessness. However, it is also true that one has to compete with aspirants who have devoted much more time for the same preparation and on an average are better prepared due to peer feedback.
Depending on one's personal conditions including financial woes, parents' pressure/support, motivation, ability to risk one has to take call whether or not to prepare while in job. It is generally preferable to devote 1-2 years fully to UPSC than slogging it out in a 5-year along-the-job plan. If one is really determined to do it while working, then take care to devote 3-4 hours daily to UPSC without fail. At this rate one might be ready in 2 years. Don't do it without a plan. The plan should not be monthly or weekly. One must have a daily plan. whenever you try to satisfy yourself with a monthly plan, you are fooling yourself. You will have to come out of your comfort zone. There are no shortcuts.
This all for now. In a nutshell, I would say the following things:-
1) Stop looking for best strategy, best tip, best book list. Get down with the books in hand and start studying.
2)Do not look for shortcuts.
3)Preparation for UPSC is painful and boring barring a few subjects. Learn to live with it.
I hope my words are of some help.I will be happy to answer any further queries.