There's a million and one theories out there.
Your K/D will place you in the skull rank given you have more than 2000-3000 kills to your name.
To achieve the next one you will just need to string ALOT of awesome games in a row where you do plenty of revives, open doors and overall be a good team player.
I only have the Skull and Knife with that stats... :
I'm on PC and it's impossible to make a new account.
I'v 128,24 K/D and i'm better than a lot of shootgun...