If you pick a root note along one of the inner strings, then choose the other notes of the minor pentatonic scale adjacent to or behind (closer to the headstock) the root note, this pattern is called the BB King box. For example, on the guitar, picking a G-note root on the 4th string 5th fret, at that same 5th fret you automatically get a 4-note on the 3rd string, and a 5-note on the 5th string. To finish out the box, you can back up 2 frets from the 4-note on the 3rd string to get a 3b note, and back up 2 frets from the root note on the 4th string to get 7b note. Similar for mando and banjo, except modify for how your strings are arranged. Enjoy!!!