I think I just answered another of your questions.
As for ATL, if you are staying on the same airline, it is generally simple. There are 4 or 5 horizontal concourses connected by an underground tram system. If there is no change of airline, the connecting flight is usually in the same concourse. Ask the gate agent for connecting gate info or look at the monitors. Every now & again, the gate info will change, so check again at the gate. This happened to me on Northwest at the old Detroit airport. Got sent to the wrong gate & missed my flight (their fault).
I think Delta has 2 concourses, so that might mean taking the tram to another, also easy to do.