ORIGINAL: gamespooker
If I'm by myself (which i usually am) i get the head, or antlers up on the tailgate. then while holding the deers head or front feet on the tailgate i wiggle my way onto the tailgate as well. once you are in the truck and have a hold of the deer it is much easier to slide them on up. The adrenaline of loading a nice buck helps too. I have had to drive back to the house and get the tractor before, in that case i just slide them on the mower.
Exactly what I do. I'm about 6' 2" and 225 so once I have a hold of the rack/head, I can pretty easily bring the deer on up into the bed of my truck.