If you are new to Stumbleupon, or have never heard of it, then a good place to begin is here: http://www.stumbleupon.com/aboutus/
To begin, you will need to:
- Have downloaded and installed Firefox.
- Have a Stumbleupon account.
- Installed the Stumbleupon toolbar.
Go to the shortcuts tab. My favorite configuration is to use Ctrl + the arrow keys to stumble and rate pages, so that hand only does minimal movement, although the same thing can be done with other keys.
Hit "OK", and you should be good to go.