If you have any additions to contribute, please send them in. These are not ramp plans. It is a small FAQ about ramp building. If you are looking for ramp plans, try Heckler magazine's web page.
Nails are cheaper and easier, but screws generally work better.
Use drywall screws instead of wood screws. I would highly recommend that you use screws for the surface, even if you nail the frame together. If you want to, you could even use pool coping. Use one continuous piece of coping on each side instead of several small pieces. Also, when designing your ramp, make sure you have the correct amount of flat bottom.