Phase-1
English- All Previous PO papers and RBI papers with timed tests
Math- All Previous PO papers and RBI papers with timed tests and cover all basic topics in mathematics such as Numbers, Time Work, Probability, Distance, Speed, Data Sufficiency, Ages problems etc. Books for RBI prep are available but I did not have time to read them. Covering all previous PO and RBI papers itself takes time. This year the math pattern was slightly different.
Reasoning- All Previous PO papers and RBI papers with timed tests
General Awareness- 2 newspapers everyday (Hindu and Economic Times/Business
Standard/Business Line), learnt basics related to RBI like Repo rate, reverse repo etc, functions of RBI, current governors, deputy governor and other basics about our economy. Most of the questions will be from newspapers.
Phase- 2 (Consumes lot of time. Better to start before pre-lims results are published if your work is hectic).
I used material from RBIGB, Datt and Sundaram for few topics and the internet for economics and finance. For management I used L.M.Prasad and Principles of management by Dr.G.K.Vijayaraghavan and M.Sivakumar. L.M.Prasad seems too lengthy but u can grasp and write on your own. The second book is too brief but has all the topics in a concise format.
The most important thing is to cover every topic. For economics there is no guarantee that you'll do well in the exam even if you cover every topic. It is equally important to be abreast with recent economic developments, especially ones pertaining to RBI's decisions and policy action, inflation management etc. You should be able to argue, discuss about it. Even then you may not be able to answer all questions. But since the pass mark is based on comparative performance it won't be a problem.
For English read essays from a good essay book. Essay carries a lot of marks and could be general (internet) or technical (inflation management etc). Learn model question types from previous papers.
Tip: from phase-1 grasp concepts in general awareness without cramming. Your knowledge will increase tremendously by the time you are done with RBI and it will pay off no matter where you decide to work.
Interview:
Interview is only for 50 marks but not to be taken lightly. It is a panel interview and is technical. The only way is to be thorough with newspaper content and grasp all the concepts. You should be able to explain whatever you say.
Interview is like an X-ray. lol. What you know will be very evident. So learn as much as you can about RBI, our economy, newspapers, your work exp, and general awareness questions like how you'll raise money for business etc. If you prepare well for phase-2 it helps here too.
All the best. I would advise have a back-up plan because seats are limited and failure does not mean you are not good enough.
Most importantly- Pray to God. Whatever happens happens for good.