Mine are:
Breathing in for three heartbeats, out for four, repeat while counting backward from ten, repeat.

Focusing on one object or shape in my mind and denying all other thoughts.

Imagining my mattress is on the sea, waving from foot to head or head to foot (switching gets too distracting and requires mental focus that seems to NOT be relaxing). This one might freak you out at first because it really feels like your body is flapping up and down. Super cool.

Simply noticing my skin as it expands with each heartbeat, on my nose, my feet, everywhere, area by area. Once you learn to feel your heartbeat in your skin, you can do it on the bus, at work, anywhere.

Like the commenter in today's blog post mentioned, imagining cold liquid/mud sliding down my head, from the top of my brain to the bottom. Super effective.

So what are your favorite meditation tricks?