My friend and I arrive to the HK airport (by international flights) with a 40-minute difference. Where is the best place for us to meet? I've heard that all flights arrive to terminal 1. Is it a good idea to meet at some specific place in Terminal 1, before going through the immigration and customs? If so, where exactly? (The map says there are 8 levels, and I'm not sure which level and place is most optimal.)
For arrivals, everyone gets out of immigration control at the same place, I believe. I usually ask friends to meet me at the Ho Hung Kee (何洪記) restaurant, because it's easy to spot (you'll see it almost immediately when you get out of immigration checks). If you arrive in the morning, it is also a great (Michelin 1-star, actually) place to get some breakfast.
Update (04/19): I now have reservations about the quality of the restaurant, but it still serves as a good place to meet. Or the Tai Hing besides it.
It is better to pass through immigration separately, as the immigration counters are spread over the whole width of T1.
Exchange flight numbers with your partner. When you pass through immigration, there will be screens with the luggage belts for all current flights. The first to arrive can pick up luggage and go to the other traveler's luggage belt and wait there.
There's Wifi all over the airport. You can update each other about your status.
If one flight is very late, the traveler on time can pass through customs, and head to a landmark to wait. There are a few international places, easy to identify. Pret à Manger, all the way to the left when you come out. McDonald's, about in the middle of the arrival lobby. Etc. Pick one and send you friend your location.