In our bedroom, our hammocks are attached to the ceiling joists. On the large hammocks, this is pretty easy since they like lots of sag. On a typical camping hammock, it wouldn't be as practical.
In my gear room, I've got some chain that runs from the ceiling joist to the footer of the wall. The chain is vertical and there is one in each corner of the room. I use these vertical chains as trees by simply clipping my biner into one of the chain links. Super easy and will accommodate any hammock I want to put there. The distance between 'trees' is right around 12'. There is a video on it somewhere around here.
Here it is: