I make two lists, one with what I want to read, and one with whatever I feel most in the mood to write at the time. Then I treat the lists entirely differently. On the requesting list, I only nom the ones that are super rare, because I figure no one else will ask for them. On the writing list, I only nom the ones that I am pretty sure are just popular enough that if they're in the tagset someone will request them. I tend to offer a bunch of other things in the tagset too, mind, but I'm usually in the mood for a certain style of canon to work with, so it helps to have plenty of available options that suit.