As long as the club you have a membership with is in on the same concourse (or before suck-urity) as the airline you're flying (and you, of course, have that club membership), then you're all set.

For instance, AS and AA are out of the same concourse at SEA (C & D); as a member of both clubs, I prefer to use AS' boardroom on the days I'm flying AA (free wireless & hi-speed internet, yummy snacks, free booze, etc). Flying AS out of MIA, I'll use the AA AC, as there is no boardroom there. Comes in handy.