Automatic completion of common functions in TeXShop?

According to About TeXShop (available here)

"Auto completion is user configurable. To configure, open the file ˜/Library/TeXShop/Keyboard/autocompletion.plist with TeXShop. Read the comments at the top, edit appropriately to redefine Landweber’s choices or add your own, and save. Be sure to edit and save in UTF-8 format if you use Unicode characters".

The source editor supports command completion. Type the first few letters of a word and hit the escape key. The remaining letters will be entered. Hitting escape again will cycle through all possible completions.