1. Thank the topic.
2. Post your gamertag and sub to [ Register or Signin to view external links. ]
and wait for the invite.
3. Join the invite, then back out.
4. Go into split screen with the checkerboard map, and start it.

Back button= Rank 55
Dpad Right= 0 prestige.
Right Stick= 1st prestige.
Left Bumper= 2nd prestige.
Y Button= 3rd prestige.
RT= 4th prestige.
LT= 5th prestige.
Left Stick= 6th prestige.
X Button= 7th prestige.
B Button= 8th prestige.
Dpad down= 9th prestige.
Dpad up= 10th prestige.
Dpad left= 11th prestige.
Look at the ground= Unlock All.
5. End the game, go online and see your prestige.
6. Come back and post legit.