Make Your Guitar "Cry" With a Wah-Wah Pedal

There are a million devices available to add various effects to the sound of your guitar. Choruses, flangers, distortions, delays, octave dividers, harmonizers and the like.
Most effects pedals work by pressing a button or a foot switch which actives the effect. Once activated, the device will "color" the sound of your guitar and be "fixed" according to how you have the parameters set on the effect.
The one effects pedal that operates differently is the wah-wah pedal. This pedal requires the user to activate it, and in addition, control it while playing, all in real time. It's truly an "interactive" type of guitar effect.
A wah-wah is an "old school" effects pedal and has been around since the sixties. One of the early users that brought the pedal to prominence was Jimi Hendrix.
Unlike many of today's digital based effects, a wah is an analog pedal that is nothing more than a glorified tone potentiometer mounted to a variable pedal controlled by the user.
When the pedal is in the upward position the tone is "rolled off" and will produce a muted sound. Advancing the pedal to the complete forward position will produce a high end, almost shrill, tone.
The pedal gets its name from the fact that when you advance it from the upward position to the most forward position while playing a note, it will produce a note that sounds like a "wah". This "crying" sound is the basis for the name of the most famous wah-wah pedal, the Dunlop "Crybaby".

Here are a few ways you can put your wah pedal to good use:
As a Lead Guitar Tool
The wah can be used as an "expressive" tool for leads. Used effectively you can almost make your guitar "talk". Listen to "Voodoo Child" by Jimi Hendrix or Stevie Ray Vaughn.
As a Rhythm Guitar Tool
It can also be used as a rhythm effect and was closely associated with guitar rhythms of the disco era. Think Shaft!
As a Tone Control
One almost overlooked way to use the wah-wah pedal, however, is as a "set it and forget it" external tone control. By scrolling the pedal to find a slightly rolled off tone and leaving it there, and combining that with a touch of distortion or crunch, you can arrive at a nice Santana-esque sound.
Considering the amount of sweep in the pedal, the tonal possibilities using it this way are endless.
There is a bit of an art to using a wah pedal and it takes a little practice to learn how to use it effectively. But if budget is a consideration and you are limited to only a handful effects pedals in your arsenal, a wah-wah should definitely be one of your first investments.