These are the magic notes. Slow blues in the key of E. Start off with the B on the 2nd string, 12th fret. The next note is bent up about a quarter-tone (it's a blues note, whatever sounds like the blues to you). This is the flatted seventh, in between the D and the E flat, one of the classic blues notes. Then you return to the B before jumping up to the E string and making another quarter-tone bend at the 15th fret. This is the flatted third, the other classic blues note, in this case between the G and the A flat. Don't release this bend slowly, just pushup the string until the G becomes a blues note (again, let your ear be the judge), and then quickly release the bend and hit the E note at the 1st string 12th fret. This is a classic B.B. King style intro, a very simple lick that to me is the essence of the blues, it all depends on bending the strings just enough to get that "blue" sound. Don't rush and concentrate on your tone.