If you need more info, look into the site high impact halo.
You must be an elite. You cannot be host. You get into the passenger seat of a warthog. then hit x to get out, but right after, before your character exits, start hitting b repeatedly. This cancels the exit. You have to keep hitting b or you will get out. On everyone elses screen you will get out, but on yours you will still be in. Another player can even get in on top of you. You are then driven to the enemy base and then you get out. Once you are out, if you walk at all, you will return to your body that got out earlier. When dummied you can only punch others, grab flag, etc. You won't be seen, and can't die, unless they find your original body that got out and kill it. There, now you know how it is done, and also how to stop it.
Forums are for help, not flaming people.