First You need to Find the best exchange when it comes to security, order execution, speed, availability of coins, users, volume on the coins and last but not the least the User Interface
No. 1 Bittrex
Bittrex is the best when it comes to Performance
No. 2 Binance
Binance is best when it comes to User interface and user support
No. 3 Poloniex
Poloniex is a very Reliable exchange which has established its name from the past