Check the manual it will tell you what the High rates and Low rates should be on the plane for all surfaces. If your radio is computer driven you can even toggle them in flight. As to setting the rates, first it's usually it's easier with two people. One holding the ruler and doing the adjusting and the other moving of the controls.

This is the process for one control surface: (depending on how many you have you will need to repeat this that many times)

1. Place the plane level in a stand and ensure the control surfaces are centered.
2. Taking a sturdy ruler and mark (visually or with tape) on the ruler where the center point of the control surface is.
3. Then move the surface up. (The distance up should be the rate noted in the manual.)
4. Repeat the movement a few time to ensure consistancy and accuracy.
5. Do the same thing for the down it should be of equal rate.
6. After you get the throws where you want them move to the next control surface and repeat.

Hope this explains it well enough.