Neil Shubin's Your inner fish (a pretty cool book, I might add) discusses this briefly in the introduction. From memory, it's a question of combining geological

Neil Shubin's Your inner fish (a pretty cool book, I might add) discusses this briefly in the introduction. From memory, it's a question of combining geological knowledge with knowledge of what you want to find. Basically, you're looking for rocks that are likely to preserve fossils and of the correct environment (no use looking for deep sea sediments when looking for humanoids, for example) and the correct age for the fossils you're interested in. Now that you know more or less what kind of rocks are relevant, you can look at geological maps and find places where these rocks are exposed (and not, say, buried 2000 metres below the surface).