First of all, try to know the market value of the vehicle before buying. It can be done by asking individuals who works at automobile shops.
Secondly, choose the bike which satisfies you the most.
It is better to avoid the motorcycle which has been registered on more than 3 users.
Vehicle conditions should be checked with a mechanic if possible.
Tyres should be fresh.
Always search for bikes which doesnot run many kilometers.
By getting the market value try to bargain as much as possible.