I've come up with a way that's really fast to set up, especially if you know your knots. If you don't, you can substitute almost all knots with some form of hardware if you prefer, but it's really worth learning the knots to reduce gear. They're all also useful in many other places (for example, I use the round turn and two half hitches to tie my guy lines to my pegs).
For this setup, you won't need very much gear:
* 10m (33ft) of kernmantle cord (rock climbing rope). I use 5mm rated at 6KN (600KG static load), and it's a good idea to not use cord much weaker than this. There is actually a hell of a lot of force put on this rig to keep it all taught. 10m leaves me qith quite a bit spare, but I woudn't go below 8.5m
* Several small karabiners. The ones I use in the pics are 600KG rated ones from Kong, but as long as they'll easily cope with the weight of the gear you're hanging, you'll be fine.
* A (hammock) tarp. I use an ENO ProFly I bought on eBay. The nice thing about this fly is that it comes with tensioners attached to the guy line attachment points, making setup easier: you can just loosely tie the guy lines then tension everything once it's all positioned.
* Tent pegs. I use some made my DAC, they're super strong and light. I won't be showing the tarp pegged out, I assume that's too obvious to bother with.
* Hammock (Optional). This setup will work just as well for someone who's lightweight camping with just a tarp instead of a full tent.
The image below shows the final setup, without the pegs (because I was too lazy and kneeling on damp ground in jeans is no fun). My pack is hanging under the tarp so I could do a lot of this setup in the rain and keep it dryish.
Step 1: First tree
There's not much need to be too cautious about how big the loop around the tree is, as long as it's not tight around the tree. The smaller the loop, the more force is exerted on the rope.