Keeping a guitar in tune has been the fateful frustration and sometimes awesome ruination of so many guitarists that it’s about time some information be spilt. First off, if your guitar will not stay in tune, there’s some things which would be handy to check: (1) it may be that your strings are worn, torn, dead, imperfect or just plain dirty and old; (2) the neck of your axe may be warped (you can sight down the fingerboard of the guitar and check this out; if there’s any kind of bow to it, it’s time to take it. to the hospital); (3) the bridge may not be located in the right place (the distance from the nut to the 12th fret should be equal to that distance from the 12th fret to the bridge); or (4) it could be that your tuning gears, sometimes called machine heads, are worn and will not keep the strings taut.