The ukulele, although it only has 4 strings instead of the 6 or 12 on a guitar, can still be difficult to tune if you are not accustomed to stringed instruments. Tuning a ukulele can be done in a number of ways - read below to find one that's right for you.
Steps
Part 1 of 3: Know the instrument

Step 1. Memorize the tuning of the strings
The most common ukuleles, the soprano and tenor, have their 4 strings tuned to SOL DO MI LA: G below middle C (low G), middle C, E and A. Each string is stretched or relaxed using a wrench that is at the top of the handle.

Step 2. Look at the tuning keys
To correctly refer to the strings of your ukulele, hold it in front of you with the neck pointing up. The lower left key is the G string, the key above grants the C string, the upper right key grants the E string, and the key below grants the A string.
- You will turn the keys to change the tension of the strings and therefore modify the notes produced by the strings. The direction in which you need to turn may vary between instruments, experiment. Generally, the meaning is the same for the two keys placed on the same side of the instrument.
- Stretch the string to raise the note, relax the string to lower the note.
- Do not over tighten the strings. This can seriously damage the instrument and the string can break.

Step 3. Find the location of the strings
The strings are numbered from furthest to closest to you, assuming you are right handed. The first string is the LA string, the second is the E string, the third is the DO string, and the fourth is the G string.

Step 4. Familiarize yourself with the boxes
The frets are separated by small metal bars called frets and are numbered from the clefs to the body (center) of the instrument, with the fret closest to the clefs called the first fret. Pressing a string on a fret when playing the string changes the note up.
Part 2 of 3: find the pitch of the notes

Step 1. Choose a reference instrument to tune your ukulele
The easiest way to tune your ukulele is to tune your strings by adjusting them to match the notes of another musical instrument. You have different options: a piano, an in-line tuner, an electronic tuner or a whistle tuner. You can start by tuning only one string with a tuner (and tune the rest of the instrument based on that string) or you can tune all strings using a tuning reference, instrument, or tuner.

Step 2. Tune using a piano (tuned) or keyboard
You press the keys and play the corresponding strings on your ukulele, adjusting the string with the key until the ukulele string makes exactly the same note as the piano or keyboard.

Step 3. Tune using a whistle tuner
You can use either a round chromatic tuner or a whistle specially made for the ukulele, which looks like a small pan flute. Blow into the hole corresponding to the desired string, play the string and adjust the key until the string produces exactly the same note as the whistle.

Step 4. Tune using a tuning fork
If you have a tuning fork for each string, you can hit each tuning fork and adjust the corresponding string until it produces exactly the same note as the pitch. If you only have one tuning fork (usually the LA 440), use that to tune the corresponding string and then tune the other strings based on the first one.

Step 5. Tune using an electronic tuner
There are two main types of electronic tuners. One type of tuner plays a sound (a note) that you need to play with a string, the other type of tuner "listens" and analyzes the sound of the note you play on the instrument and tells you if the note is too high or too low. The latter is certainly the easiest way to tune especially for beginners, who have difficulty differentiating between the pitches of notes. It is also the tuner generally used by professional musicians.
Part 3 of 3: tuning the strings

Step 1. Tune the G string
Tune the G string (the string closest to you) until it is well tuned.

Step 2. Play the LA
Place your finger on the second fret (second fret from the top of the neck) on the tuned G string. This note should be an A, and the same note produced by the string farthest from you is the A string.

Step 3. Tune the LA string
Tune the A string based on the A you produced with the G string while playing the second fret. They must produce exactly the same note.

Step 4. Play a G on the E string
Place your finger on the third fret of the E string. This will give you the G note, it is the same note as the open G string (without pressing a fret). If the 2 notes are not identical, it is because your E string is not well tuned.

Step 5. Tune the E string
Tune the E string (pressing the string on the third fret) so that it plays exactly the same note as the G string open.

Step 6. Play an MI on the OD string
Place your finger on the fourth fret of the DO string. This will produce an MI.

Step 7. Tune the DO string
Tune the C string based on the note produced by playing the fourth fret of the E string, it should be the same as the note of the open C string.
Advice
- Changes in temperature affect stringed instruments and will affect the tuning of your ukulele. Don't be surprised if your instrument goes out of tune after being outdoors.
- Consider purchasing a humidifier for your ukulele to help it stay just right after you've tuned it.
- When tuning the strings, try to complete the tuning of each string by turning the key up, not down. This will make the instrument stay tuned longer.
- Some ukuleles have trouble holding the tuning (staying tuned). If it doesn't stay tuned, take your instrument to a luthier or music store to have it tuned.
- When playing with other ukulele players, decide which ukulele is going to serve as a reference and tune the other instruments based on that reference so that they are all in tune with each other.
Warnings
- Do not over tighten the strings. You can damage your instrument.
- After you've tuned all the strings on your ukulele, you might find the first string slightly out of tune and need to tune it again. This is because stretching or relaxing the other strings caused the neck of your ukulele to move slightly and caused a small change in the tuning of your first string.