Open string or extraneous noise is often overlooked. It is a real problem for guitarists who play with high gain or large shows. There is no secret losing the noise, you just know it has to been done. The first thing is to watch other guitarist. After that start exploring. I will tell you that it is a two handed job. The left hand is pretty obvious, you can use the fingers to mute any string beneath the one you are playing. I.E. If you are playing the 6th string your left hand can control all the other strings. With practice you can use this technique on the 5 string learning to let the top of your left hand finger mute the 6th. A little tricky but a little practice and you will have it. From 5 or 4 down is when you need to let your RH do the work. The guitarists that really taught me to mute out unwanted sound were Frank Gambale and Steve Morse. Steve's RH is amazing. You can find him talking about it on You Tube. While Frank uses the left and then right hand as you move to other strings. Hope this helped. Although in time you mute as second nature, at first remember it is a constant problem.