Most guitar players don't change their guitar strings like every week or two that the more active players do. So then this matter of cleaning you're guitar strings becomes something important to do. Now why is that?
Well if you have been playing guitar for a while you might have noticed a build up of dirt on you're fretboard, most of that is "collected" around the frets on the guitar. It can turn up like this black or green deposit on the fretboard.
Also if you are reading this and using an ordinary computer mouse. Chanses are that you have a build up of some similar dirt on you're mouse. Go ahead, look on the sides of you're mouse where you rest you're fingers.
The guitar strings will collect this dirt also. The dirt that's been accumulating over time is a mix of skin oil, skin and dirt. You can't really see it that good. But it's there. Having you're guitar strings clean is important because it will keep the guitar strings in their best condition. Increase the life of the strings and also help you play smooth. The sound of you're guitar is also hurt if you play with dirty strings. The tone and sustain of you're guitar will be less with dirty strings.
Now you can use a sheet of towel or cloth and fold it around the guitar strings. Move up and down and apply some pressure to remove the unwanted dirt from you're strings. You can also use an brush to get the dirt that's collected in the guitar string grooves. An while you are at it you could try and clean the fretboard, but this is easier to do at the same time when you put new strings on the guitar. I have more on this at the link below.
Now some people say that you can use WD-40 oil to clean the guitar strings and also get a cleaner looking string. Now it does work I have found. But WD-40 is a silicone based oil and that means it will stay around for a long time. And also it will get on you're fingers, fretboard, neck of the guitar. And also anything you touch will get the oil on it. So not such a good thing to do. There are special oils to buy at the shop that will do the job much better.
I hope that this was helpfull to you. And if you like you can continue to read more about how to change you're guitar strings if you click on the following link.