Outside stimuli are your friend! Just...have stuff happen to them. Preferably in really public places. Maybe they're carrying a lot of stuff and drop it, maybe they lose something and have to go poking around for it.
Basically, try to set it up so circumstances set up the interaction, and you might have to do less work getting your character there.
Re: cont - general ; withdrawn characters
Basically, try to set it up so circumstances set up the interaction, and you might have to do less work getting your character there.