I am a student of B.E. 5th sem...i want to prepare myself for GATE exam but there are no coaching institutes in my town..what should i do???

What town are you in ? If you can manage studying online then there are such courses offered by some institutes and correspondence is also an option. Now as you are in 5th Sem already so I'd suggest start studying your current syllabus seriously as GATE paper consists of 2nd sem-6th sem syllabus. O

you can prepare for GATE exam yourself , you can purchase any good book for gate exam

Buy some branded book, and start to prepare.