Caroll, since you are asking about shifting, I assume you are referring to 3 octave scales. The way I was taught to shift for scales was start your first finger on the firt note of your scale (ie for a G or A scale you would be in first position, but B starts in second, C in 3rd, ect). You would SHIFT on the A string after 2 fingers.
For example, a G scale would be:- G string 0,1,2,3 -D string 0,1,2,3 -A string 0,1,2 SHIFT on A 1,2,3,4- E string 1,2,3 SHIFT 1,2,3,4
The other scales would vary shifting once you get to the E string to 1,2 SHIFT 1,2 SHIFT 1,2,3,4
Mmm hope that doesnt look too confusing!