UPDATE (03/28/2010): Thanks to all who commented for some nice ideas!
Step 1: Prepare
If you don't want to make dough at home, see if your grocery sells fresh dough (usually in bags, usually near the deli). It may not be easy to find a good brand, even if it's made in-store or locally. I've never tried the frozen bread dough, nor the stuff that comes in a tube. Call me old-fashioned, but good pizza does not start in a tube! If you're at a loss, try your local pizza shop. A dough ball will probably cost only a couple of dollars.
Here's a general rundown of what you need:
1. Dough (a.k.a.: flour, water, yeast, and salt) Also see step 2
2. A pizza pan, or baking stone and pizza peel (if you're using a peel, you need fine corn meal or dried bread crumbs), plus an oven to put it in.
3. Toppings: crushed tomatoes, cheese, veggies, meats, etc.