Watch the Thirds in C: 1 online guitar lesson by Brad Carlton from Guitar Lab: Thirds and Sixths

This lesson will take intervals of thirds out of the C major scale and demonstrate their layout on the 3rd and 2nd strings. This pair of strings are the only pair on the guitar that are tuned a major 3rd apart. You'll only be dealing with 2 shapes: the major 3rd where both notes are in the same fret, and the minor 3rd where the notes will be in adjacent frets.