I own a Hennessy Hammock Backpacker Asym (31 oz.) which is a very popular model amongst hammock hangers. To get into it, you enter it from below, standing up in a slit that runs half way down the middle on one side. Once inside, you lean back and sit on the half that does not have the slit, raise your legs and lie back. The edges of the slit are covered with velcro and close together under your legs. To get out, you press your feet on the velcro seam which will open below you, stand up and slip under the hammock to get out.
Back in my tent days I remember going through a similar routine every summer: I’d wake up in the morning and feel like I needed to get up and out of the tent as quickly as possible even if I was still tired.  The sun would quickly be turning my tent into a sauna and I’d find myself moving into a camping chair by the fire pit, waiting for other people to wake up and go through the same process so we could all sit around and talk about what rock or root had kept us up during the night (or marvel at the one person in the group who slept great and seemed to possess an almost superhuman ability to sleep through, and on, anything).