My method:
Bring water to a steady, rolling boil.
Put the bushings in the water and let them boil for 3-5 minutes.
Fish the bushings out of the water with a spoon.
Put them in your truck immediately.
Tighten your truck down as far as you can.
Go outside, make sure you have a skate key with you.
Push around, make sure to carve a bunch.
Loosen the truck until it feels right.
Voila. Your trucks should feel pretty much broken in by now.