I feel a little superficial for writing this, but honestly I think its something fairly important that no one really talks about. I mean the whole dress for success thing. Writers are notorious for being unsociable basement dwellers, but it doesn't have to be that way, and the way you dress can play a part.
If you want to be a celebrity novelist, dress that way. If for you that means pencil skirt suits, great. If for you it means black skinny jeans and vests, awesome. If it means shorts, flip-flops and t-shirts, wonderful. The key is to dress nice in whatever style it is you like. I kind of like attention, so I like the idea of dressing to get that attention. You are an interesting person who deserves to be known, and your attire can help make that known to the world.
Also, the right clothes can do awesome things for your confidence. I have huge self-confidence issues, but when I feel like I'm dressed nice and look pretty good, it's a lot easier for me to put myself out there. It makes me feel stronger, and more willing to take risks. There are lots of ways to learn how to dress your body type. Take advantage of what God gave you, both your mind and your body.
I know this is kind of a weird subject for a writing blog, but like I said, I'm thinking along the dress for success lines. Even if you're a shy, like many writers are, you can't get away from the need for attention just to sell your work. This includes stuff like signings, television interviews, writers conferences, book tours, etc, and in these situations you're selling yourself almost as much as your work. Obviously fashion is not one of the important things about being a writer, but I think its something that can be used to your advantage in your writing career.
Hope this helps. Let your clothes work for you!