Examine the above diagram. These are frets, centered around the root in red, that B.B. plays extensively. King will bend many of these notes, however, to change their pitch. For example, in the key of A, B.B. likes to play the 2nd string, 12th fret (the note above the root in the diagram) with his third finger, which he immediately bends up to the 14th fret. He'll then often follow that note with the root note, the 10th fret on the second string (with a healthy dollop of vibrato, of course).
B.B. often plays the lowest note in the above diagram with his second finger, which he then slides up two frets to play the other note on the third string. Then, he'll end the mini-riff with the root on the second string. This is a really common B.B. phrase, one you'll hear in almost every solo he plays.
Another favored B.B. lick is playing the highest note in the pattern (in the key of A it would be 12th fret on first string), then bending it up two frets. From there, King will often return the string to it's unbent position, re-play the same fret, and end the lick with (you guessed it) the root.
