Every electric guitar has knobs to control its sound. Often, music fans and even amateur guitarists believe that it's the amplifier and preamp effects that are largely responsible for a guitar's sound. While this is true to a certain extent, a guitar's volume and tone knobs can be used to alter the instrument's sound, long before the preamp and amplifier come in. Depending on the brand and model of your guitar, it will have at least one volume and one tone knob and may have more of each.
Plug your guitar in to its preamp effects, if applicable, and the amplifier itself. Turn the guitar on.
Turn your volume and tone knobs all the way to the bottom. They are typically marked with the numbers 1 through 10 for reference.
Set your amplifier's overdrive channel to at least five, or any setting that you typically use to achieve a thick overdrive sound. Set the amp's volume knob high enough so that even when your guitar's volume is set to two or three, it will still be audible through the amp.
Turn your volume knob all the way to 10, but leave your tone knobs at 0. Pluck a note or play a chord and, as it rings, slowly turn your volume knob down. You'll notice that the overdrive sound will appear cleaner before eventually weakening. This means that if your amplifier's volume and overdrive settings are high enough, you'll be able to change the sound of your instrument just by tweaking its volume knob. Experiment with different sounds using the volume knob until you are aware of its full range.
Turn your tone knobs up to 10, play a note and notice the sound. When both knobs are turned to 10, the guitar's tone will be on the thin side. Play another note, and slowly turn one knob at a time down to 0. You'll notice that in the tone knob's middle range, your sound will get beefy and thick. When you reach 1 or 0 on the knob, the sound will be clean. Now try turning the other tone knob to change the sound again.
Experiment by playing different notes and changing the volume and tone controls. When you're familiar with the sound you can achieve through these simple tweaks, try switching from one pickup to the other and see how the sound changes.