Well, there's a school of thought that you shouldn't have any physical description of your characters whatsoever, but personally, I like to know a bit about what the people I'm reading about look like. To do it without it appearing contrived, though, that's the problem; stuff like "I swept the brush through waist-length ebony tresses and studied my reflection critically in the mirror, noting that my new black patent-leather corset and elbow-length lace gloves served to enhance the sparkling violet of my eyes" is going to make your readers roll their own eyes and gag, while no description at all can be kind of frustrating.
One option is to bring it into the reaction your narrator gets from other characters, e.g. "The guy at the end of the bar had been staring at me for a quarter-hour now. Either he was really into tall, flat-chested blondes, or I had some broccoli from dinner stuck between my teeth," or "I did my best to keep up with Larry, but his legs were a good ten inches longer than mine, and at twice his girth I was tiring fast."