The best thing to do when your guitar tone is already dull and lifeless is to put a new set of strings on your guitar. Guitar strings are harder to keep in tune when they are old and dirty. Aside from the bad sound that they produce, they are more likely to break and even harder to play.
It is important that you replace them regularly and do not think that strings cost too much because there are cost-effective strings in the most popular gauges. If you have a specific brand in mind, you might as well buy them in packs because this is a great way to save on strings. You can also check out affordable Savarez guitar strings at Musicians Friend. The strings are vital part of your guitar sound. In fact it is the vibrations of the strings that create the sound of your guitar. When the strings are dirty and old, they are more likely to produce flat and lifeless sound.