Boredom during lectures

During lectures of teachers, parents, bosses, etc. how do you entertain yourself without appearing like you're tuning them out?

Just try to convert their conversation into something intresting

Stare at them blankly and nod every once and a while.

I generally just start thinking about something else without even realizing it (no I don't have ADD)...like said about just keep looking and nodding or w.e and think about what you're doing later that day or if you remembered to call whomever back, whatever...