The simplest is a camera on a tripod if you can get it high enough.
Better would be mounted on the wall/ceiling intersection with a $15 mount from Amazon. But then you'd still need to supply power, climb up and down a ladder to access the memory cards, etc.
I have my camera mounted up there, but it is wired to my Mac tgat lives on a shelf under the camera that I can reach. It records directly to my computers hard drive, and I start and stop the recordings from the keyboard. Not simple to set up, but very easy to use.