Mine are pretty 'laxed... first and foremost, no drugs and no smoking.
We have to have some things in common, like our sense of humor should click. Nothing is more annoying than sitting there laughing at a TV show or a movie while your GF sits there silent, rolling her eyes. Then you find out that she thinks Ryan Seacrest or the women on The View are hilarious. No.
While we don't have to share interests, an understanding of one another's passions is important. Obviously, I like video games, and my GF, while not a "gamer", loves hearing about why I love gaming, and she understands the kinds of games I like and what about them I find appealing. By the same token, she loves to read (I like reading, but not to the same extent), so when I hear her talk about the nuance of certain writers, it's an incredible turn-on and is also intellectually stimulating. I can also show her a video of DJs like Klever, Craze, Qbert, etc., and while she doesn't know anything about DJing, it'll still be fascinating to her, and she'll ask how they did a certain thing or made a certain sound. That kind of interest in what I like (and vice versa) is really one of the most rewarding.
Physical attraction is important to me, but she doesn't have to look like my avatar to get the nod. People might not agree, but like Jules said, personality goes a long way. I really believe that, but I wouldn't lie to myself and put *all* of my eggs into the personality basket.