How do you tune a guitar?
There are several techniques.
If you're a beginner I'd suggest investing in a guitar tuner, some acoustic electrics have a built-in tuner but in any case a guitar tuner shouldn't set you back more than 20 USD.
In those rare moments when you don't have an electric tuner readily available (even the professional musicians I've toured with carry one around), provided your low E string (the thickest or top string) is in tune (you can do this with a phone app, a keyboard [tune it to the 12th note below middle C], or a frequency generator website to tune your low E) you can tune the other 5 notes. In order to tune your low E you need to play the low E string at the same time as your app, website, or keyboard note until any dissonance (the "wobbly" sound you hear if you're out of tune) goes away (at this point your low E is in tune). Once your low E is in tune you can easily tune the other 5 strings, here's how:
- To tune your A sting (string below the low E) depress the low E string on the 5th fret (this note is an A) and pick the low E string along with the A string below it, if there's any "wobbly" noise, adjust the A string until the "wobbliness" disappears
- To tune your D string (the string below A) place one of your fingers, usually the index, on the 5th fret of the A string (this note is actually a D) and play both the A and D strings, adjust the D string until the wobbliness has disappeared
- To tune your G string (the string below the D) you depress the D string on the 5th fret (a G note) and play both the D string and the G string, remove any dissonance and your G is in tune
- The B string is a little different, this time you're going to put your finger on the 4th fret of the G string (a B note), then play both the G string and the B string at the same time removing any dissonance
- To tune your high E string (smallest string) place your finger on the 5th fret of the B string (E note) and play both the B string and the high E string at the same time
Eventually you'll be able to tune by ear, unfortunately the ability to tune by ear isn't really something that can be taught, it's more something that comes with general familiarity with the instrument. After 6 months (if you play every day) you should be able to tune by ear!
I hope this helps!