Bear in mind that I learned to use clipless pedals on a bike with a freewheel, but here's what I did:

1) Loosen tension on pedals all the way.
2) Stand over the bike and practice clipping in and out a bunch of times with one foot, then the other.
3) Ride the bike around deserted streets slowly while clipping in and out with each foot. Don't actually stop, just clip in and out while riding along.

That was about it. I felt pretty comfortable after about five or ten minutes of riding around my neighborhood. The next day I commuted to work and I haven't looked back since. In the beginning I was consciously telling myself to be ready to unclip when I came up to red lights. When I started riding fixed a year ago, I didn't find the transition to clipping into a moving pedal to be all that hard.