With a little extra geometry you can control your sub-d model a little more. Here is a really nice trick I just learned. To follow this tutorial you should have some basic knowledge of how to select polygons and points. Everything else we will try and cover so you can understand the thinking behind to work.

Step 1 - start out with a polygon that has four points. When you press the [tab] key you will get a nice circle like shown in the following image.