Everyday people go about their lives expecting things to go pretty much the same way every day. When I notice people stuck in the "same old routine" I give them a compliment.
Maybe it's their appearance, how they do their job, even the sound of their laugh. It makes them feel good and for a moment yanks them out of the mundane into a world of possibilities.
Find something most people don't comment on, act like you just can't help telling them, be honest and sincere, then go on your merry way. Easy!
(Space it out and try not to hit the same person twice or it will go from happy to just plain creepy!)