This process is usually done with an object capable of strangulation such as a belt or for the pros, an actual noose
It is usually recommended that the chokebater has a "spotter" in case of emergency, but this concept basically defeats the art of masturbation.
Friend 2: What is?
Friend 1: Seriously its like nothing can turn me on anymore when I'm trying to bate.
Friend 2: Do you ever watch like super hardcore shit, like snuff films or whatever.
Friend 1: No man, I'm not that weird. Its just that there is something missing.
Friend 2: Well, I heard Tony tried that one thing where he put a noose around his neck and right before he was about to pass out, blew a huge load and said it was the coolest thing ever.
Friend 1: Chokebate?
Friend 2: Yep, thats it
The action can physically be seen in:
"Weeds" on Showtime. Kevin Nealon as Doug in Season 5.