Document, Document, Document!
I work with some pretty complex MVC code, and am only now actually understanding how it works, as opposed to accepting it on faith. Whenever I make a change that I have a hard time figuring out, I put a comment in the code at that section to help clarify what is happening. It might not have helped me since it wasn't there, but it'll help the next person around. I also like to ask other programmers around me to look at my changes to see if they are clear.
My company has an internal wiki that we use for documenting a lot of the meta tasks we do, like virtual server problems, common queries, etc. Whenever I come across something I've not done before but will have to do often, I check to see if there's a wiki on it. If there isn't I'll make one. More people have gotten involved in it as well recently, so I hope it will grow faster. I think it really helps communication of the more mundane tasks we have.