sir i m engineering student of 1st year mech. branch i want to prepare for gate exam right now what i have to do?

prepare well by taking training in any good institution and start preparing from now.

I will advice you focus on your First Year studies at present. You should prepare GATE or GRE or GMAT in Final Year or in Third Year. Focus on First Year and Second Year. A good score of FE and SE will give you good base which will help in GRE, GMAT or GATE preparation later.