First, if your just doing this because you want to be cool, stop right now. If you don't, and you are new to the skateboarding world, read this. Hope this helps!
Step 1: The Clothes
Be yourself. Don't wear skate clothes all the time because you might be called a poser. Just wear a simple shirt with a logo, some jeans, and some skate shoes. You'll need rubber soled shoes. And not DC's.