I like to run my campaigns sort of like a videogame. I'll have a grand campaign arc of sorts, and then little side "quests" that the PC's can choose to invest in or not. I usually make these side quests more personal or character driven. So, an assassination for the assassin, maybe a wanted criminal for the huntsman, some black market intrigue or political stuff, a magical artifact or lost ruin rumor, etc. Or, if a character has some ongoing background/personal thing, I'll drop something about that into the stew.