I'd had the idea to do this for months. I live in an apartment with a balcony and every time I go out onto it and see the wooden boards and their angle in relation to the door frame, I think of doing a cliff photoshop.
I setup the camera on a tripod and took some sample shots of me lying horizontally, hanging onto the door frame and pretending to be hanging from something a lot more precarious. When I reviewed and was happy with the angle, I took some timed shots of me and brought the best of these into photoshop. I then cut myself out and pasted myself into a decent photo of a cliff scene I found online and added shadows, lighting and adjustments. I also liquified my face a little to make it seem more terrified.