Hey,

This is the basic pattern for the blues scale. 
Once you learn this pattern just slide it up and down the neck. 
The root note of the scale is the note that the scale is.

Alex

G major

e|-------------------------3-|
B|---------------------3-6---|
G|---------------3-5-6-------|
D|-----------3-5-------------|
A|-----3-4-5-----------------|
E|-3-6-----------------------|