I often face this problem: Let's say I'm on the 12th fret of the G string with my index finger placed on it. Now I want to move on to 12th fret of the B string, so basically just below the one I was pushing down. The problem is that everytime I move my index finger from the G string to B, the open G string plays. It's just one of many other situations similar to this that happens like all the time.
I try to figure it out but maybe you know some techniques that just work and I can apply to my playing. I'd be bery happy if you could share them with me.
Several ideas. If your fingers are damp, it can make an open string re-sound as you take them off. You may be inadvertently moving your finger sideways, so plucking the string with its tip. (Quite an advanced technique!). By using a different finger, it's good to release the original gently, but still keep touching the string, so damping it. Be careful not to sound the 12th fret harmonic here though. A lot of players damp unused strings with their plucking hand palm. On electric a good way to hone this skill is to turn up the volume, and/or use overdrive, so some feedback is created, then use palm-muting to quieten all unused strings.