KATL prefers a western operational flow, but east flows are quite common nevertheless.
West ops: North Runway Complex: Arrivals on 26R and departures on 26L During busy hours, a large percentage of 26R arrivals are routed all the way around the far end of 26L via B, V, and then brought the gates via F. However, aircraft with longer wingspans are not permitted on V (767s are the only heavies that routinely use it), and must cross the runway elsewhere. South Runway Complex: Arrivals are mostly on 27L and en route to the gate are often routed all the way around the end of 27R via N, P, L. Runway 28 is used as overflow at peak times (particularly arrivals from the south), as well as for Cargo arrivals destined for the south cargo ramp. Departures are normally from 27R, which is the longest runway at the airport, and thus is preferred departure runway for heavies on long routes, and is also the default runway for emergency landings.
East Ops: North Runway Complex: Arrivals on 8L and departures on 8R. Arrivals either follow B, V, F, or cross 8R and proceed to the gate via F Departures taxi to runway via E. South Runway Complex: Arrivals via 9R and 10. Departures via 9L (and occasional cargo departures on 10 as well). 9L departures normally taxi via M and take off from intersection M2, so as to allow 9R and 10 arrivals to use P as an end-around and follow L to the gates. If there is an unusually big backlog of departures (as may happen after a weather delay), Ground will send some departures up N, have them cross 9L at P, and then head them back down M to M2 from the opposite the main departure stream coming up M from the other direction. This does work quite well in Tower3D if you are meticulous with Hold Position and or Hold Short commands.
-You may choose to not activate Runway 10/28 for arrivals in the game menu. Instead, just activate 27L/9R +26R/8L. Then use the ENTER FINAL command to side-step planes to 10/28 when the final corridor on 27L/9R gets too crowded. Likewise 26R arrivals may be sidestepped to 27L if there is space.
-Departing ground traffic en route to 27R may lined up on both L and M if needed. Traffic on M may then depart from intersection LB, and alternates departures with traffic on L which departs from the end of the runway.
-Note that there are two taxi lanes in each of the ramps between terminals T-E. These do not operate like two-way roads, with planes passing each other on the right. Instead, an aircraft will always use the lane that is on the side closest to its gate, regardless of whether heading north or south. Forgetting this detail will result in head-ons between departing and arriving aircraft. Unlike in the real world, there is no way to instruct an aircraft to switch lanes in order to go around another plane here, even if there is room.
-Taxiway D (In the game it is called Delta, but IRL it is referred to as "Dixie" so as to avoid confusion with the large number of DAL aircraft based at the airport). This is the only route for crossing between the North and South runway complexes (contrast with KLAX which has multiple options for this). On the KATL Airport Diagram, it is marked as a non-movement area, but this does not mean that it is closed to traffic. It just requires a specific clearance for any aircraft to traverse it (much like crossing a runway). In the game, it is just treated as normal taxiway without any special restrictions, so do plan taxi routes carefully to avoid nose-to-nose situations here.
-Taxiways SC and SJ are a pair of parallel North-South taxiways used for to getting to and from Runway 28/10, which is separated by some distance from the rest of the South Runway Complex. SC is used for aircraft traveling TO this runway. SJ is used for aircraft traveling FROM this runway, heading toward the main terminal area. This mirrors the normal U.S. driving convention of staying to the right side.
-Tower!3DPro players will find it very beneficial to take advantage of the program's "Vacate Runway" command to assign specific runway exits to arriving aircraft. If used strategically this will serve both to get arrivals closer to their assigned gates, and also help prevent backups onto the arrival runway during busy sessions by separating them onto different taxiways. It will also help avoid logistical problems caused by smaller aircraft that by default tend to turn off early, using the high-speed taxiways going in the opposite direction of travel.