Okay, at the risk of sounding terribly uncultured, I just found out that it is customary to tip the "Skycap." I have a few questions about this, because the only thing I know about this is that it is the person who helps you with your luggage, and the usual is about $1 per bag. So my biggest question is: when do you tip him/her? Before? After? I don't want to make the person uncomfortable and have one of those awkward moments.
My other question is: are there any other people I should be tipping, and how much? Where I'm from, the only people you tip (that I know of, anyway) are those who serve your food, and the delivery guy.

Help!