I've always used Bittrex an my go to exchange. I know there's many out there, but I don't like to have many accounts for the same purpose. Mostly trade AltCoins here, and so far Bittrex has done me well. But as a tip, doesn't matter what exchange you use, keep your coins in a wallet that you own. Not on an exchange.

I dodged a bullet when MintPal was hacked.