In Writing Solid Code[0], Steve Maguire recommends stepping through every line of code, in a symbolic debugger.
Sounds crazy, but I usually end up doing that, anyway, as I work.
Another tip that has helped me, is to add code documentation to inline code, after it’s written (I generally add some, but not much inline, as I write it. Most of my initial documentation is headerdoc). The process of reading the code, helps cement its functionality into my head, and I also find bugs, just like he mentions.