One of the most important techniques that we need to achieve control over our legato technique is a good solid muting technique. Again, this technique will be beneficial to you whatever technique you are employing but as discussed before, the focus is in the control of the left hand.
This exercise starts with the index finger of the left hand hammering on from nowhere to the 5th fret of the 1st string followed by the 2nd finger on the 6th fret of the 2nd string and then we repeat. The goal with this exercise is to mute any strings that we are not using.
I like to follow a basic rule that we can apply to make sure that we are muting all unwanted strings. In the main the left hand will shoulder most of the responsibility but the right hand does come into play.
1: any strings above(pitch wise) the string we are playing will be muted by the left hand.
2: The lower adjacent string will be muted by the left hand.
3: Any other strings will be muted by the right hand.
With this exercise, the first note that we play will require the finger we are using (index finger) to lightly touch the adjacent string so that it is muted. The remaining strings will be muted with the right hand. The following note which is played by the middle finger mutes both the 1st string and the 3rd string and the right hand mutes the remaining lower strings. Once you have control over this exercise you can then move on to different strings in different positions
Once you have established that basic rule you will be able to control the muting of the strings wherever you are on the fretboard giving you even more control. It is in these techniques that your control will move up to another level.