I prefer a 0-5 scale, because if I give myself too many options, I can't seem to rate myself.

So for me:
0 = no anxiety (not sure this one has ever actually happened!)
1 = slightly worried thoughts, no physical symptoms, can easily move on to other thoughts
2 = Difficult to dismiss worried thoughts, they're starting to loop in my mind. Still no physical symptoms
3 = worried thoughts are starting to turn to "worst case" and unable to dismiss them. Rapid breathing, slightly elevated heart rate
4 = Definite physical symptoms, rapid breathing, elevated heart rate, shaking hands, still able to stay present and function
5 = Full blown panic attack, dissociation, unable to stay present or function