One thing I always look for before any other thing is fast withdrawal. I don't like waiting hours or even days just to get my money in my wallet. I like whenever I place a bet and win, let my money be available within few minutes of me hitting the withdrawal button. And you should consider how safe the website is, and try to know how they work.

An example is Nitrogen Sports that allows users to make use of an anonymous account and if you don't create a password to secure that account immediately, then you will lose, as well with your money if you have already deposited in it. Another thing I look for is a site with good support for their customers.