There are actually two airports, domestic Hartsfield (south terminal and north terminal) and Jackson (international terminal). Inside the compound, for ticketed passengers, there is a train between domestic baggage claims and concourses T, A, B, C, D, E, F (international). On the outside, there is a bus between the international terminal and domestic shuttle port.
Arriving to domestic: Take the train except maybe from terminal T, even if the moving sidewalks are tempting. The South and North domestic baggage claims run parallel, with ticketing at one end and the exit to the shuttles (and to MARTA subway which is very visible) at the other. There are many shuttles there, but the information is good. Groome Transportation should be in the first row, and your ticket email will have the information. The waiting area is nice, for an outside bus port that is.
A good meeting place in domestic for people wanting to hook up with somebody at the airport, e.g., coming on different flights, accessible to non-ticketed visitors as well, is at the clock in The Artium.
Arriving to the international terminal: It may take up to an hour from landing to go through the customs and getting the luggage. In a typical situation everything is clear: a long walk to passport control, waiting in lines, getting the luggage, exit making sure to follow the signs to ground transportation, not to connecting flights. Do not leave your luggage behind in the international terminal. Not picked up luggage will go to Columbus first by plane and then by ground transport to Auburn. Occasionally, international flights land at domestic, but the luggage goes to international. There are at least three international baggage claims, one specifically for Montreal. Just follow the signs. To get to the shuttles from the international terminal, take the connector bus (ca. 15min ride).
Departing from the international terminal: Groome Transportation drops off at international if asked. To check in, taking an international flight, particularly if first leg is domestic, you may need to go to domestic as not all airlines have counters at the international departures. Airlines with counters at international (in addition to domestic), see picture taken last Fall.
