The way Rob described it is definitely the most common one you're going to hear. I usually start wrapping earlier, when I'm in the hole or even a little before they call bar is loaded for that guy two in front of me. That's usually right on time for me, though I like to be on the platform the very second the bar is loaded.
I take at least two warmups in the wraps for feel, and because I like to gradually tighten the wraps so as not to be thrown off by an extremely tight wrap. Two or three warmups with my belt as well. The closer I get to a meet, the more I lean on my gear. I think it's great to work without wraps in the offseason, but in prep I'm belted and wrapped very early on in my training to perfect the technique.
I don't wrap my wrists for squats, but I don't lever my belt until they're done wrapping. Can't really set the belt while I'm sitting down, either.
Edit: Saw that's what Rob said, I actually start wrapping a little after I'm called as four out. My wraps are very long.