I started a tradition about a year ago. Whenever I make a recipe from a cookbook, I take a thin black sharpie and write the date next to the recipe. Now, I'm not so presumptuous as to assume that my copy of HTCE is going to be a family heirloom someday *cough, cough*...but already it's nice, as I flip through my cookbooks, to see the dates written it.
It's also handy to simply acknowledge which recipes in a book I've already tried.
See? Now I'll always know that I made this on Andy's birthday, 2008!