The map shows all available new quests you could pick up, and whichever current ones you want it to. If you don't remember what quests you're in the middle of doing, you should probably read through your quest journal anyway. That will explain what each one is about, what your next objective is, and it's location (if it has one). Just select the ones you want to do next.

I do wish they'd raise the maximum number you could select though. Even just raising it from 5 to 6 would be nice for beast tribe quests, which come in groups of three and might have a couple groups whose areas overlap.