If you were lucky enough to buy a Marshall Rock-Kit, you will already have a Korg Electric Guitar Tuner. If you didn't, or you don't have it with you, you can download wav's of each of the notes to tune each string to.

Shown in the diagram (left) are the open-string notes for the guitar, written in the treble clef. The corresponding strings are indicated below on a 'chord window' (for an explanation of chord windows please see Lesson 1). Learning these notes is an important step in learning to play the guitar. The dots shown on the window are the positions on the fingerboard that will produce the same notes as the adjacent open strings. This is called Relative Tuning and is useful if don't have a tuner or instruments nearby to tune to.

Relative Tuning
1. Tighten the 1st string to the correct pitch (approximate if a tuner or other instrument isn't available).
2. Tighten the 2nd string until the note on the 5th fret is equal in pitch to the open 1st string.
3. Tighten the 3rd string until the note on the 4th fret is equal in pitch to the open 2nd string.
4. Tighten the 4th string until the note on the 5th fret is equal in pitch to the open 3rd string.
5. Tighten the 5th string until the note on the 5th fret is equal in pitch to the open 4th string.
6. Tighten the 6th string until the note on the 5th fret is equal in pitch to the open 5th string.

Next you should check each string again, in case any of the strings have noticeably loosened, as they may do when first used.