A standard blues scale looks something like this.
E 3--6
B 3--6
G 3-5
D 3-5
A 3_5
E 3--6
This is in G but you can put the scale anywhere using the note on the 6th string for the key- ie, you play it at the fifth fret and it's in the key of A.
It's a bugger to learn but, practice it up and down (low to high) mess about with it and you see the solo of Stairway becomes much less dificult (so does most classic rock and or roll).
just remember 3 fret spacing for strings 1 and 2 and all the others 2 frets except 6 which is 3 again. This made sense when i started it. :)
Accuracy,you say? hmm interesting concept..