I've always been concerned about the efficiency of my left hand's movements. Visually, it's easy to notice when fingers move too much while they're not playing notes. It's more difficult to feel when this is going on, and it's impossible to hear it. So I often watch my left hand for stray fingers during practice.

I recently got thinking about a more methodical approach than simply watching my fingers. Restricted to a single string, there are three possible positions for each finger: fretting a note (fret), resting on the string (rest), and off the string (off). A finger in the fret position should apply no more force than is necessary to play the note without buzzing. (A great exercise for this is outlined at GuitarPlayerZen.) Fingers in the rest or off positions should be as relaxed as possible, either barely touching the string or just far enough to allow the string to vibrate freely when necessary.

Four universal rules can be deduced:

• Only the finger playing the current note should be in the fret position, otherwise I'm wasting energy.
• Any fingers higher than the fretter should be off, or the note won't sound.
• There's no reason for the 1st finger to take the off position unless playing the open string.
• There's no reason for the 4th finger to take the rest position unless it's playing the next note after a real musical rest.

Whether the fingers lower than the current fretter are in the rest or off position depends on the situation. This is where it gets tricky (as tricky as a silly thing like this can get, anyway). There are times when it's best to rest everything behind the fretter, poised to fret their own notes at any moment. For example, when playing fingers 4 3 2 1, the first note has finger 4 in the fret position while the other fingers should be resting on the string, ready to play the following notes. There are times when some fingers below the fretter ought to be off the string, as the next note might require it. For example, when alternating between fingers 1 and 4, fingers 2 and 3 needn't touch the string at all.

Now, since I don't believe in new ideas without charts, I made a chart. I took all the permutations of four fingers on four frets and recorded what position each finger should take during each note. I cleverly encoded the positions as follows: fret = f, rest = r, off = o. The numbers denote the order of the fretting fingers. Each group of letters denotes the positions for fingers 1-4.

1 2 3 4
f o o o, r f o o, r r/o f o, r r/o r/o f

1 2 4 3
f o o o, r f o o, r r/o r/o f, r r/o f o

1 3 2 4
f o o o, r r/o f o, r f o o, r r/o o f

1 3 4 2
f o o o, r r/o f o, r r/o r/o f, r f o o

1 4 2 3
f o o o, r r/o o f, r f o o, r r/o f o

1 4 3 2
f o o o, r r/o r/o f, r r/o f o, r f o o

It's often ambiguous how the 2nd and 3rd fingers should behave; I used r/o when the rest and off positions would both work. It's up to personal preference how to handle these, but I suspect the rest position is usually least taxing.

I've started practicing these chromatic sequences once in a while, and I keep this approach in mind whenever I'm watching my fingers for efficiency. It's already working its way into my normal playing habits. The idea can also be applied when changing strings and playing chords. I just slow down any given passage enough to consciously prevent fingers from pulling away from the fretboard when they shouldn't.