THIS IS A QUESTION FOR EXPERIENCED TRADERS IN BITCOIN
I am an experienced trader in other markets and would like to trade the Bitcoin market on both the long (buy) side and the short (sell) side.
Can someone point me in the direction of the three biggest exchanges that allows me to go long or short the BTC/USD
Seems like you are a stock or forex trader.If you do like to trade BTC/USD then try SimpleFX since you can able to trade up bitcoin on there and at the same time you can able to trade with Forex and commodities.
There are famous exchange on here on cryptoworld but they are just focusing on crypto. Try poloniex.com or bittrex since these are the famous exchangers as of now. Shorting bitcoin movement is somehow difficult if you are not experienced enough to be an active trader.