Gangwars. If you've played SA, then you know what this is about. Plus there's some bike stealing and Stubbs deals out some pretty interesting jobs. I guess if you want to waste your time with arm wrestling and the high and low card game, there's that as well. You don't have to take anyone anywhere if you don't want and if you do you don't have to drop them off since they all basically live at the clubhouse. Taking various Lost members on missions though is a good idea since you can build up their combat stats.
IMO, if you can't get into Lost and Damned then you probably never a fan of GTA to begin with. Even with the shortened length, I've had about as much fun with L&D as I did with SA.