Don't leave your engine running. I try and do all of my engines cold. Some people say warm is better, but I get them pretty darn clean while they are cold.
Cover everything electrical. Alternator, distributor, relays, fuses, etc... Some of this is not required, but if your asking me for advice, I'm going to tell you to cover everything electrical. Any polished peices need to be covered up(degreasers will discolor these peices). Don't use high pressure water. Don't be afraid to use a scrub brush.
All items that were covered up will need to be done by hand after you're finished washing the rest of the engine.