When the cartilage layers in your ear seperate, they fill with blood, causing a massive amount of swelling and leaving room for hte cartilage to move around and reset. When the blood finally drains out, the cartilage is left in weird patterns, hence the horrible pictures. When you drain it, you should massage it out and kind of crunch up the cartilage in the ear to make it look normal again.
I've been told you can actually help prevent it to a degree by massaging your ears everyday. I know that when I had cauliflower ear, I had to have it drained and then rubbed out, which sucked.... bad.
After I had my ear, an old wrestling coach told me to start massaging my ears to get the cartilage soft and it's less likely to happen. I do know my ears feel softer since massaging them regularly. I've had my ears folded over and ground into the mat and forearms and since I started doing the massage thing, it doesn't hurt and hasn't cauliflowered on me.
YMMV.
PS. for a REALLY BAD example of cauliflower ear, do a google search for Wallid Ismael... I've been told that he's partially deaf in the one ear (you'll know which one) from the cauliflowering.