I know that the ground floor/roadway is for Arrivals, but near which area or stand (denoted by letters) should a driver wait, to avoid parking (I know that lengthy waits are discouraged)? Does the origin of the arrival matter? If so, where should a driver wait for someone from Asia, Europe, ...? I tried this.
If you have a cell phone with you and your party does too, use the Cell Phone Lot. You can wait there for up to 45 minutes. Your party can call you on arrival and you can tell them your car color etc and come forward to meet them. The large posts outside are numbered which should help you connect. They can tell you what post they're waiting at, for example, and you can work your way to that number.
At Terminal 1 the doors are labeled, inside and out, with letters:
The large concrete posts are numbered D1, D2 etc. You can just barely see them in the posts at each edge of this picture:
If you can't talk live, pick a post number in advance. Your best bet would be a reconnaissance trip a few days before, then email or call them at home with your chosen post. Apparently international arriving passengers can get taxis at D1 and limos at D3 from Terminal 1. So D2 or D4 sounds promising, but it's probably better to pass through yourself and see. I seem to remember that the innermost three-lane segment - the one showing in these pictures - is for taxis, limos and shuttles only. Passenger cars I think have to use another lane with different post numbers. That's why either going there yourself to look, or having them call and tell you where they are standing is better than you trying to tell them where to stand.
Finally, you could just park in Express Park ($5) and go in, and wait inside at International Arrivals. People clear customs and come out of a single door where you should be able to spot them, help them with their luggage, and go together back to Express Park.
I thought to supplement user Kate Gregory's supernal answer above.
Founded upon personal experience, I can confirm that the post number C is immediately in front of and thus closest to International Arrivals. I'd estimate the distance to be less than 30 metres. To wit, once you exit International Arrivals, C is simply outside the array of glass doors in front of you, and cannot be missed!