I don’t know why I hadn’t thought of it in these terms, before, but this morning just before a lightning-speed class I suddenly realized that if you have a good article in hand, you can look in four “directions” for more articles like it. (I use “article” because that’s what I was working with this morning, but it works for anything with citations, I guess.)
You can move backward by mining it’s bibliography. You can move forward by using Web of Knowledge to do a cited reference search. And you can move side to side (sort of) by reading it with an eye both for content and for vocabulary that you can use when constructing future searches.