Grab your guitar. Before you learn an alternate tuning, it is important to understand the standard tuning of a guitar. On a six-string guitar, the sixth string is the thickest string located at the top of the guitar. Get out your guitar tuner and tune this string to E. Working your way down, tune the fifth string to A, the fourth string to D, the third string to G, the second string to B, and the first string to E.
Choose an alternate tuning. A common alternate tuning is Open D. To tune your guitar to Open D use your tuner to tune the sixth string to D, the fifth string to A, the fourth string to D, the third string to F#, the second string to A, and the first string to D.
Strum your guitar. Notice that even though you are not touching any of the strings to form a chord, your guitar is playing a D major.
Experiment. Now that you are in an alternate tuning try playing different notes to see how they sound. Though all of the rules to playing guitar still apply, playing chords will change based on the tuning. An E major chord, which is made up of the notes E, G# and B, will still use those same notes in an Open D tuning, but those notes are now in different locations compared to where they were in the standard tuning.