When I teach hand quilting, I recommend a size 8 for beginners. Personally, I like a size 10 and can't manage a size 12 at all! I recommend using a PVC style quilting hoop (frame) in the 11X17 size and you will want a thimble with a safety ridge around the top. You can find good pictures online by googling "how to hand quilt" or looking in a basic quilt book like Fons and Porter's Quilters Complete Guide.
Taking a class is really the best way to learn this skill, because then you can see the motion involved. You want to focus on learning the rocking motion and getting that rhythm rather than the size of each individual stitch.