FIVE simple steps:
1) make sure that you have last stand on at least one of your classes
2) be in a game but be willing to have a 0 k/d spread.
3) What you do is hold a special grenade and get put in last stand
4) Just sit there and it is now a frag, you can either throw or hold it.
5) The trick is that you can be in a fire fight and just pull out a special grenade and get downed but hold it. (they get no points for it blowing up on you)
Have fun and i'm sorry that i don't know how to make videos (i'd love a walkthrough). XD