If I'm bored at work, school, doctor's office, etc. I'll visualize a beam of light coming from somewhere, and then mentally place mirrors around the area to get the beam of light to go where I want it to. Up stairs, around corners, etc. Sort of like some video game puzzles where you have to rotate mirrors a certain way.
If I see ZIP codes, phone numbers, license plate numbers, etc. I total the digits in my head and see if they add up to a multiple of ten. If they do, I sort of think, "heh, awesome," and then go back to what I was doing.
I'm very particular about the freshness of what I'm eating. If I have any doubt at all whether something is or isn't still good, or if crackers/chips/whatever are even slightly stale, I won't eat them.