On Lockout go to the sniper tower. Go to the area by it where the mountain and the ramp meet. Crouch in the spot and jump out. Look right for a downhill ramp and jump to where the flat part meets the ramp. If you get lucky you can do a double bounce by the tower. On my game, I always fall off the edge though.
Go to the sniper spawn by the fan in the middle of the tank spawn and the warthog spawn, Then go by the fan in the corner on the left side. Crouch and walk forward until the screen shakes. Then jump, turn 180 degrees and run for the ramp. Jump and before you hit the ground you will fly up diagonally. Of you do it right, you will fly up the side of the fan. Move to the right a little and you will get up to the fan. There is another way to get up without superjumping. Here it is: Go to the bridge that you can blow down. jump down and let the fan push you to the top of the bridge while it's up. Then use a gernade or rocket to blast yourself onto the fan. On top of the fan is an exelent position for a Juggernaut sniper, because he has unlimited ammo. Anyway, when you get up blow down the bridge and no enemies can get to you. The only way is to use a sniper or well thrown gernades.