I have found that once you get used to it, sleeping on a hammock is much more comfortable than on the ground. Furthermore, you will never have to worry about a ground tarp, uneven, rocky or wet ground, and can probably eliminate your tent as well as some other gear.
Please note this is a guide for beginners, and does not cover more of the technical aspects of hamocking. If this guide has gotten you interested and you want more information on hammocking I suggest you go to the Hammock Forums, you'll find a ton of completely neurotic and awesome people obsessed with hammocks, with a ton of information on all things hammocks. I'm currently planning revisions for this instructable based on the methods that I learned from HF and now use myself, but for this guide should be adequate.
Step 1: Gather Materials
one foam sleeping pad (yes, those cheap, foam sleeping pads you swore never to use again after you got your inflatable pad)
I will be providing to you:
a basic knowledge of knots
A note on hammocks: buy a good, light hammock. No heavy braided cotton line. I got a lot of use out of my Amazonas Traveler before it tore through (don't let it drag on the ground!). When I bought it I paid around $20 at the local sporting goods store, look around and you should find one similar. There are also many options for making your own hammock, and plenty of commercial options. I recently got an ENO Singlenest, which I like a lot so far.
A note on Carabiners and rope: use only load bearing carabiners, designed for climbing. These carabiners end up supporting much more than your weight depending on how tight you string your hammock. For this same reason, the golden standard for rope in the hammocking community is Dyneema, or Spectra, which are incredibly strong, low stretch materials. I now use 7/16" Dyneema that can hold something around 5000 pounds and is very lightweight. Paracord works, but Dyneema would be preferable. Nylon rope will stretch and poly rope won't.
Step 2: Prep your Cord
first take the cord and cut it into two pieces, about 6 to 9 feet long (2 to 3 meters for those of you using metric. i envy you and your national standards...).
to tie a loop in each end we will use a figure eight on a bight. If you've sprung for dyneema you shouldn't do this, go ahead and follow instructions elsewhere on making whoopie slings, single-line-suspensions, utility constrictor ropes, or whatever.
take about 5 inches on one end and double it back, this is a bight. take the bight and tie a figure eight with it. a figure eight is nothing more than a regular overhand knot with an extra half turn in it. please look at the pictures as it is truly difficult to tell how to tie a knot with words. your loop should be big enough to fit your carabiner inside. If you don't like my instructions there are excellent, new-fangly pictures, instructions, and such here.
Do this to both ends of each rope, 4 times in total. by the end you should be pretty good at tying a figure eight on a bight.
There are many, many methods outlined in detail at the Hammock Forums. I don't use this method anymore, but it's fine for beginners who don't want to spend hours and hours coming up with a hang system.
Step 3: Set up your hammock
wrap your parachute cord around the tree tightly enough that it wont slip down. how do you wrap it around? however you want, that's whats great about the rope you made. you can wrap it once, twice, tie a ravens head, feed one end of the rope through the loop, any way you can make it work on your tree. just keep in mind that any knot you tie and sleep on will probably not come out very easily. parachute cord is not easy to work backwards with (but you should be able to get away with not tying any knots, just loop it around and put your carabiner in the two end loops).
now take your carabiner and put it through the loops in the cord. put one end of your hammock on the carabiner. repeat for the other tree. your hammock should hang in a gentle curve, you don't want a huge sag as your rope, hammock and trees will bend and stretch as you settle in.
Many people have expressed concern about the rope damaging the trees. Here on the west coast most of the trees I hammock on are huge and tough, and paracord wrapped around them doesnt seem to do any damage. If you live somewhere where your trees aren't as hardy and have thinner bark, you could use flat webbing for climbing or polypropylene truck straps. Just wrap these around the tree a couple of times and hang your rope and hammock from that.
Step 4: Get comfy and enjoy the outdoors!
You may have noticed that we have yet to used the foam pad. This is where we need it.
Once your hammock is all strung up properly you are ready to sleep in it. Take the foam sleeping pad and slip it inside your sleeping bag. This is very important. without it your body will compress your sleeping bag filler and reduce it's R value (how well it insulates). your entire backside will be very cold without any insulation from the air. The sleeping pad will keep you comfortable.
If you're really into hammocking you can get an underquilt, which is a sleeping bag that goes under the hammock to keep you warm, eliminating the foam pad.
Step 5: Not a step, just useful thoughts
Again, there are many, many different ways to hang your hammock, go ahead and experiment and find what works best for you. This is just to illustrate how easy it is to get started hammocking.
Please, share your thoughts in the comments below. Thanks!!