For example, let's take the case of flight Qatar Airways QR 738, which departs from SFO airport.
Searching the flight number on Google will indicate the departure terminal, not the check-in counter aisle:
The SFO official map doesn't mention Qatar Airways:
How can I know ahead of time in which aisle the check-in counter will be located at the airport? (Ahead of time = anytime before reaching the airport, so that I can minimize walking time to reach the proper aisle).