When I'm hunting on my land, I haul the deer in a small trailer attached to a garden tractor. The trailer bed is about a foot above ground, so it's not hard to drag the carcass on board, using a plywood plank for an inclined plane.
I drive the tractor alongside the rear of my vehicle, and it is less than a foot from the trailer bed to the tailgate of my vehicle.
It's nice to have help, but not really necessary with this setup.

Drag them up onto th back of my ATV. From the back of the ATV into the pickup bed. Easy peasy! Lots of things are possible one step at a time!

I lower the tailgate, and put the back feet (or antlers) where I can grab them from inside the truck. I bend at the knees, look up, and do the same motion I would doing squats in the gym, utilizing my leg muscles to do the work. I lean back as I do it, dragging the deer in and letting the tailgate take the brunt of the weight.

seem*

I'm not a big guy...155lbs. A number of bucks I've shot have come close to out weighing or outweighed me. I keep two 2" x 6"s 8 feet long boards in the back of the truck and drag the deer up. It makes it simple...the other option for someone who isn't 6'4" 250lbs but is pretty fit is to grab them from behind, under the front shoulders and wrestle them in using your legs and body weight to do most of the work. It's not graceful but it gets them in.

I can attach a block and tackle to the roll bar on my Jeep Wrangler, tie the legs together and hoist 'em in the back (no back seat or carpet, and I have a tarp to control any blood---VERY necessary.)

I am lazy, I got a loader tractor. I drag a deer to the edge of the woods or field, then drive the tractor out and lower the bucket, slide the deer in and drive the truck once at the truck i simply tilt the bucket so the deer falls into the bed. The hardest part is climbing into the tractor.

depends...when my dads truck is available and i take that hunting its really simple. im a decently strong individual, so if i have a truck bed i usually dont have any problem muscling a deer into the bed.

now the real issue is when i have to take my jeep. the back window (i have a soft top) does not unzip so that takes a rear entry out of the equation. i have to go into the passenger door, move the passenger seat forward, climb into the back of the jeep, and finagle the SOB into the back. this is all while trying to keep a majority of the blood on the plastic i lay in the back. its pure muscle power getting him in their.

I use my 4-wheeler with a Drag Bag to camp, with lots of camp members are more then willing to help load the Deer or Hog in to our New Camp Cooler.

I usually have someone there to help me load it, but i am still realtively young and when I need to I can throw it in the back of the forester by my self.

I wheel the deer or bear out of the woods with the deer cart. Then we made a wooden ramp and take the cart right up tailgate into the truck bed. We untie the bear so the state can weigh him at the check-in station. Very simple and works like a charm.

I drive a Ford Excursion right now and it's not easy to get a big bodied buck into the back. So I tie the deer to my trailer hitch, find a drop off, get the buck on top of the drop off, and get the back of the vehicle even with the hill (a good sized drop is required). When you get there I grab him and it's easy then to do, so I just drag him into the back.