well, there's no fixed place to study for these exams ... but a good place to start is the 'Ground Studies for Pilots" series ...
which look something like this ...
http://www.amazon.com/Ground-Studies.../dp/0632059397
Get the GSP's for Meterorology, Navigation, Radio Aids, Flight Instruments and Flight Planning.
are you in india? you can get these books and more from the English Book Store ...
17 L,Outer Circle,Minto Bridge Traffic Crossing
Connaught Place, New Delhi, 110001
+91 11 23415031
+91 11 23417126
+91 11 23417936
Get hold of notes from either Seth, Buti, Surinder, Duggal. And questions banks as well. one question bank is more than enough as all of them pretty much have the same questions.
as for Regulations, you need to get this book by Win Cdr Bali and another book called the Aircraft Act 1934 ... these two books will be enough to make your head spin around a couple of times ...
when do you plan to give these exams?
what kind of a license do you have? hours? ratings?