.(probably a lot of people can do this but it's a cool trick to know)
First, ill start with an easy cliff: The cliff to the right of blue base (when looking at red base from on top of blue base). All you have to do is back a banshee into just next to the giant rock thingy up on the cliff, then jump out, while still holding d and BOOM you're up. Now lets get a ghost up. on the left side (when looking at the base from up there), you will find a little slide thing. Go down it to avoid dieing. Get a ghost and park it facing the right side of the steep ramp left of the cliff. Throw a plasma grenade at the ramp in front of your ghost, get in quickly and while holding space, go up the cliff. Once you have gotten high enough, hold d and w to strafe across the wall and you should land on the cliff. K now get off the cliff and get a banshee. Get a banshee and hover over the teleporter of red base, facing the cliff behind the base. Now make a motion where you start by going almost straight, then curve upwards and jump out so the banshee can push you through the border. If done correctly, you will be on that cliff. The only way down is death, or having a banshee back into you, jump out then u jump in. Anyways, try the same on the cliff to the right of that (when looking from the cliff at the base) only start backing into the cliff you just got on.
I hope that i helped!
