I am a 2nd year student of B.Tech CSE. What should I do after it among MBA & M.Tech? How & when should I start preparing for it?

If you are interested in technical field, and if you enjoy programming you must go for M. Tech. If you don't enjoy programming and rather enjoy dealing with people, organizing events at college etc. then MBA will be better for you. Preparing for both MBA Entrance(CAT etc.) and M. Tech (GATE) sho

The institution reputation also holds a key value. If you can do M.Tech from IITs or NITs you will get decent placement. if you score good marks in GATE you can directly get into PSUs with good packages. The same holds for MBA too. Prepare well for CAT, also write SNAP and XAT.

I think you should go for an MBA. Because, with an MBA you will earn much more compared to M.Tech.

It totally depends upon your interest. If you want to continue in technical line, than you should opt for M.Tech. While, if you want to move on to management line, than you should opt for MBA.