My best advice: Think of the earliest time you imagine a crazy person would get up so they can drop $300 on a phone. Then go an hour earlier than that. Bring a camp chair or something to sit on because you'll be standing outside for hours before the store even opens. Hopefully the people in the Apple store are nice enough to notify everyone in line where the "cutoff" is so that you only spend 5 hours in line until you go home instead of spending 8 hours in line just to be told they're sold out.
I went through this hell on the 3G launch and had to do it for 3 days in a row before I could get one. This time around, I pre-ordered and refuse to stand in a long line. I DO live in Las Vegas...too hot for lines