If you feel a pimple coming on, hold and ice cube over the area for a few minutes. That will take care of any swelling. Then dab on a little bit of clay mask (just dab in on the spot where the pimple is coming in) and leave it overnight. If you don't have clay mask, make a paste out of baking soda and some water.
If you already have a nasty pimple, I heard you can actually use Visine to get rid of redness! Squirt a few drops on a Q tip and apply it.