Spy tip: While disguised, try to hang around the enemy team for a while. Don't freak if somebody looks at you, don't look back. If they shoot you, you'll probably die, but if they pistol you once or twice, act as if you didn't receive any pain.
Demoman tip: Charge 'n' Targe + Bottle am fun. Charge at somebody (From a distance) to get the Critical bottle for a second or two, than whack. Fun.