Tuning down your guitar means to tune each string down to a different pitch. When you tune down a whole step, you tune each sting one whole half step lower than the standard tuning (A whole step is the same as 2 frets). This means going from
E A D G B e to D G C F A d.

This sounds easy but without a chromatic tuner it can be difficult. Here is a technique I use to tune down a whole step...

· Fret the 2nd fret of your low E String. Tune this note to an E.
· Fret the 2nd fret of your A String. Tune this note to an A.
· Fret the 2nd fret of your D String. Tune this note to a D.
· Fret the 2nd fret of your G String. Tune this note to a G.
· Fret the 2nd fret of your B String. Tune this note to a B.
· Fret the 2nd fret of your high E String. Tune this note to an E.

Once you have done this, your open strings will sound the notes D, G, C, F, A, and d and you are now tuned down a whole step!