I'm not a huge list maker, but I do keep a few lists running year-round. One list is actually a series of note cards that I carry in my purse. As a amateur bibliophile, I am often in the process of collecting books in a series or by an certain author. For those that I am currently working on, I jot down the titles I already own on a note card and stick the card in my purse. Then, when I find a book that I might want, I can check my list to make sure I don't already own the book. As I try to buy my books second-hand, these cards really come in handy because it can take years before I amass all of the books I'm after.
The second list is a list on my computer for gift ideas. Whenever I see something that I think my son might like, I add it to the list. I also do the same for myself. That way, DH can look at my list to make his selection when buying for me. He knows that if it's off my list I'll like it, and since I never know what exactly he will pick, I'm still surprised. A win-win for both of us!