For all you people that use a tuner to tune your guitar, you know that sometimes you just have one of those days where reaching over to grab that tuner and press that on button, takes way to much effort. To those who know what I am talking about, I recommend buying a guitar with a tuner built in or going the much cheaper way out, learning how to tune your guitar by ear.
Tuning by ear has another great benefit, once tuned properly tuning by ear is a much more accurate way of tuning you guitar.
Every so often and every time you play with someone else you will need to make sure your guitar is tuned to the proper EADGBE. This can be done with a tuner, a tuning fork, piano or another guitar. For the most part though, tuning your guitar so the strings are tuned to together is enough.
This is a simple technique to learn. We will start with the E-string that is the 6th string or the thickest string. Because it is the thickest string it is the most likely to stay in tune over a long period of time.
Hit the E-string on the 5th fret, and then hit the next string down, which is the A-string. The goal here is to make the A-string open sound like the E-string on the 5th fret. The best way of doing this is to loosen you’re A-string and then tighten it or make the pitch higher until it sounds the same as the E-string 5th fret.

To tune the D-string we will use the same technique as we used to tune the A-string. You hit the A-string 5th fret and try to match the D-string open to it.

To tune the G-string we will use the same technique as we used to tune the A-string. You hit the D-string 5th fret and try to match the G-string open to it.

We tune the B-string slightly different from the other strings. Instead of hitting the G-string on the 5th fret, we hit it on the 4th fret and then match the B-string.

To tune the thin E-string or the 1st string we will use the same technique as we used to tune the A-string. You hit the B-string 5th fret and try to match the E-string open to it.

Tuning by ear at first can 5 or 10 minutes sometimes, but don’t get discouraged, you will get better with time and practice. After you have done it for a month or two you will probably be tuning by ear in less that a minute.
If you have any questions ask them in a comment below and I will answer them as soon as possible.