I try to use the software I write.
For example one of the systems I wrote, and which I have been maintaining for a number of years now, handles subscription orders. Everytime the person that normally uses the software goes on vacation, I cover for her, and handles the orders myself. It's a boring job, but the volume is low enough that it isn't a huge burden. The thing is, for the first few years, every time she would come back from vacation, she would find the system slightly improved. There's nothing like experiencing first hand the annoyances of a system to make you improve it presto!
I try to do this with a much of the software I write as possible, even if it isn't always possible (but yes, I do use XML::Twig ;--)