Adjust the amplifier's bass and treble, EQ, settings. Continue adjusting the settings until a comfortable medium is found that minimizes the amplifiers distortion. EQ adjustments are one of the best methods for eliminating unwanted amp distortion.
Keep the guitar at a distance from the amplifier while it's plugged in. The closer the guitar is played to the amplifier, the higher the amount of unpleasant preamp feedback and distortion the amplifier produces.
Decrease the sound with the amplifier's volume control. The louder the amplifier is, the more sensitive the guitar pickups become to sound. The higher the volume, the more feedback and distortion the amplifier projects. Turning down the amplifier's Gain control to a preferred level also helps block distortion.