HOW DO I KNOW WHAT SIZE CAKE TO MAKE FOR HOW MANY PEOPLE?

If you have a Wilton Year Book, check in the back, they have cake charts. I do not use their sizes because they are to small to me.

Here's the link to the serving chart from CC: http://www.cakecentral.com/article14-Cake-Baking-Cutting--Serving-Guide---2-in-Deep-Pans.html