I’d say put together a wide variety of artwork. Work on a collection of flash type art. They will want to see that you can pull off basic flowers and cartoony stuff. Try some lettering as well. Play with lighting and shadows. Most of the stuff you do in the beginning will be very basic, till you prove your self. Its an apprentceship for a reason, some times you’ll be doing stuff you don’t care to do, but it’s all part of the game. For gods sakes don’t try any tattoo work till your in the door and given the go ahead, if you do don’t tell anyone or include pics in you portfolio. That will just piss them off and close doors faster than you can imagine.

Good Luck
Shaggs