well gentleman Im glad that I have something "new" to add to the list of suggestions here. I have no loading/unloading equipment other than myself and basic tools. (peavey, hands, chain, trailer, cart, etc. ) im always having to find a way to move pieces/logs/slabs by hand, and usually alone.
After going through adding a winch to my trailer, I still had to deal with extra battery, rigging etc.. and I had an underpowered winch to be dragging full logs up on the trailer. I used the method from the side but i dont have a good trailer for that setup. Plus the impact of logs dropping from side and hitting the deck full tilt felt like my springs were going to retire to FL. It was slow and dragging logs was messing up the decking.
I have tried pipes as others have suggested but on uneven terrain it can be a pain to push. Also up significant inclines you have to rely on separate tools to aid in pushing (come-along) or stopping it from coming back at you. (or if the log is too uneven the pipes miss in places and require repositioning often). Not good enough.
Anyways, necessity being the mother of invention I had a eureka and decided to use conveyor rollers. This is the cats meow of hand loading/unloading. I can easily load and move anything up to the max payload my trailer can carry - 2500 lbs. My conveyors hold 5000lb each. I can move slabs as is or for logs i bring a scrap offcut of osb or ply .. oddball logs no problem. My 6yr old son can push a 500+ lb chunk of wood on flat terrain and not break a sweat (ok maybe a little sweat-he sweats a lot like his dad). I have never gone back. A week or two ago I scrounged and hauled out a fresh oak stump covered in burl that was 36" dia and 48" long (and very lopsided) through very uneven forest terrain by myself. It was every bit of 600 lb and couldnt be rolled - I couldn't risk damaging the burl on the sides. Just slides right up onto the trailer and unloading couldn't be easier. Green 24" dbh cherry logs 10' long.. safely unloads in seconds. (sounding like an infomercial now). Look at this pic: 45" dia ash slab 7' long on my trailer and 8" thick! those were heavy sob's. Right up and on the trailer, and slides right off. like buttah
Oh, and to make it even easier.. those of you who have a winch (even a cheapy) can let the winch do the pulling- it is hardly even taxed.
I could go on with examples and advice but I'll leave it open to anyone who wants more info to pm me.