Turn all your amp's volume controls to zero. This will avoid you accidentally blowing out your speakers, your eardrums or giving your neighbors a heart attack.
Open up your guitar's volume controls to their maximum level. Your guitar will sound its best if volume controls are completely open.
Set all tone controls on your amp head to neutral positions. Neutral position is usually the 12 o'clock position on your dials.
Turn all your amp's head effects to the minimum. In most units, this means turning the effects dials counterclockwise as far as they go. Turn off your amp boost, if it has one.
Set your master volume level at six. Turn your volume gain dial to three. Play a few notes and check for quality. This setting should produce a nice and clean sound. Now increase the gain dial slowly until the volume is loud enough to listen to comfortably. This setting is your amp's baseline and should produce the best sound.
Reduce the master volume to three and increase the gain dial to five. Switch on the amp boost, if you have one. This setting will provide a distorted sound. You can control further the level of distortion by reducing your master volume dial and increasing your gain dial. Write down, or remember, the settings that give you the level of distortion you like. The lower your master volume and the higher your gain dial, the more distortion you can get out of your amp.
Experiment with your bass and treble dials. Sweep through the different levels as you play a song. Jot down the bass and treble levels that sound the best on your amp head. Now that your guitar amp head is tuned, you can play around with your effects controls.