Learn the blues scale in a key of your choice. The blues scale consists of the following interval pattern:
m3-W-H-H-m3-W
"m3" represents a minor third, "W" a whole step, and "H" a half step.
Practice using that blues scale over the standard blues progression of that key. The standard blues progression is generally "I-IV-V." For example, in the key of Bb, a standard 12-bar blues might use the following progression:
|| Bb / -- / -- / -- / Eb / -- / Bb / -- / F / Eb / Bb / -- :||
Consider using the other blues scales over the corresponding other chords in the blues progression. In Bb, this could involve both the Eb and F blues scale. Typically, a blues musician primarily uses only the Bb blues scale over a Bb blues progression, but other scales can be used as well.
Experiment with using both the Bb and Eb blues scales over a single chord in the blues progression. Combining scales over a single chord is one of the more common scale combination techniques. Continue experimenting with other arrangements of blues scales. There is no one right way to play the blues; as long as you truly feel the music, your blues will be real.