Very simply first of all u should be clear wht u want like u want high quality camera or whetever u want in ur phone.
Few steps
1 get to knw ur range
2 check out mobiles according to ur range
3 ask people around u which one is best mobile
4 Go to shop n check features of selected phones a. Check battery life first becoz no battery life phone be dead n no one wanna buy dead phone.
Then check its speaKers n thn ser camera
Ask for band range
Coverage qualities
Talkback estimates and other features u want in phone
5 come back now tht ur mind is clear go online n open all shopping sites like amazon flipkart ebay n snapdeal n check the price of phone n according to ur convinience order ur phone. I advise to buy online it has lots of benefits u get phone way far cheaper then market and also warranty gurantee is same for both online n offline almost. Phone buying is nt rocket science person must be clear of wht I want n holla u will nt going tl regret ur descidion.