coffeegrinder0 - note that "straps" is a very wide term. You have your basic polyester strap with a loop on one end - note that in the past, ENO's straps were made from nylon and had too much stretch. For a long time now, they've switched to less stretchable polyester. I'm mentioning that in case you also look at generic webbing for a solution. Don't use nylon.
The strap circles the tree, through the loop at one end, is cinched tight. The hammock is attached to the remaining tail via either some webbing grabbing hardware device or tying a knot.
Then there are tree-huggers. Those straps are made in lengths intended to just go around the tree and connect to a suspension line from the hammock. As such, they have a loop sewn on each end. The webbing goes around the tree, through the loop at one end, cinched tight, and the hammock connects (like with a carabiner) to the loop at the other end of the hugger. Usually, you'd need some other line - additional webbing or Whoopie Sling - to go from the hammock loop to the hugger.
Then there are daisy chains (often around 10 ft). For me, these are the simplest. The "chain" goes around the tree like a hugger, but is longer with loops sewn every 3 to 6 inches down the remaining length. You connect with a carabiner clipped between the loop at the hammock's end and the best loop along the chain to give you the desired sag.
I think ENO's chains are called Atlas straps and Kammock's chains (both sold at REI) are called Python straps (because they are long and grey).
I recommend a daisy chain if the load is on the heavy side because with the sewn loops and carabiner, there's nothing that will slip. With flat webbing, you are either tying knots or using some hardware to grip the webbing. To me, that just adds another potential point of failure to a suspension system that is approaching its design capacity.