Prepare.
Right now you are in first year, so just learn about the basic concepts of c and c++ language. Get hold on the c language .You can also practice aptitude and reasoning questions. I think the best time to join the coaching is 4th and 5th semester. You can refer these books-
DELD - R.P. Jain , Compiler - Ullman,DS- Tenenbaum,OS -Galvin, Networking - Furouzan, C - Dennis Ritchie, Architecture- Morris Mano, Discrete maths- Kenneth Rosen.
Give online mock tests.