My Tips: Skyramps = bad. If you build a midair bridge they can just jump straight over all your defenses and then book it back across your convenient little bridge.
Breaking other people's skyramps with the engineer class = fun.
Don't try to break walls with anything other than the rocketeer or engineer classes, you can, but it uses all of your ammo to break one wall.
Keep an eye on what the other team is doing if possible.
Anyone else have a few?