My luck has been on the lfotd (last flight of the day) from IAH on a Sunday evening. They are almost always booked, and they give juicy bumps -- if available. However, they have been a bit slim lately. I always check witht he GA approximately 1 hour for mainline, 45 minutes for COEX -- or whenever they post the flight information by the gate. I always carry-on and I think that is a factor....but not always. Just call CO close to departure time and ask themif the flight if oversold, and go from there.

Happy Bumps!