This cheat works best with the Scout or Henchman class but if you only wish to complete it partially any class should do.
In any type of multiplayer match(online or offline(only in the White's Estate level)) go to the area that is right in front of White's balcony. If you're in the right place, you should see in one corner an iron table and chairs. Jump onto the table and jump onto the ledge next to it. Sprint by holding the A button and jump at the last second so that you land in one of the floating gardens. It is hard to see anyone sitting in this garden so it's a nice area to snipe from but if you're the Scout or Henchman you can continue and jump to the next ledge that separates the gardens from the greenhouse(start by running towards it normally and, near the end, sprint and jump at the last second to land on the ledge. This area, though interesting, is thouroughly useless due to how easy it is to spot anyone sniping from it.
NOTE: This glitch works best in multiplayer on the same console.
This glitch can be used in any map in the multiplayer menu as long as there is at least one tall accessible area in the map. Climb to the highest point of this area with a character that has fragmentation grenades (like the Veteran or the Mercenary). Then activate one of your grenades and wait until it's about to explode. Quickly jump off this high point and make sure you die in midair. Once you come back to life look in the air where you blew up and, if the glich worked, you should see your dead body floating in midair.