Step 1: Find a CAD model of the Samsung Galaxy S3
Step 2: Start Designing
I'll apologize right now for the vagueness of this step. It is time to let your creativity flow!
The goal of my design was to hold the phone in a stable position while allowing it to rotate around a vertical axis that goes through the camera. I also wanted to be able to mount it on a tri-pod in addition to being using it on a tabletop.
Since this was my first 3D printing project I wanted to have a little fun and incorporate some of the freedom of design that you are given with 3D printing. I typically design machine parts that are milled on a CNC and have to obey the design laws that go along with that method of manufacturing.