I always have 10 or 15 different quests in progress, and I just wander around until I bump into someone that moves one of those quests forward.
Personally, I just like to shoot the shit out of the Legion's assassin squads. The .50 cal sniper rifle with exploding rounds is just SO MUCH FUN to let loose on those assholes. :-)
If Fallout:NV had a way for me to build my own shelter/town (as opposed to buying a pre-built "design" kit from Moira), I'd never play anything else.
... which is exactly why FO:4 scares me! I'll never go outside again! :-)