Do you find you switch WordPress themes a lot? If you do, Chris Pearson has taken the time to write a great post about using WordPress functions to ease the transition between themes. The idea is to put all your design elements in one file and then move the file over to your new theme every time you switch, saving you the time of re-coding the specific elements you like to see in your blog’s theme.
In his post, Chris provides the functions file to get you started, teaches you how to write your own functions, and then explains how to activate and use your new functions.
I personally have used a functions file on some of my themes, but for me it hasn’t really saved much time. That is probably because I’ve always prefered to hack my existing theme when I want to see changes, rather than to switch to a completely new theme. For people that switch themes a lot, a user functions file is definitely something you should consider doing.