First, learn the G minor pentatonic scale. (listen to this scale)

This scale has in it the note Bb, which is a minor third, or the note that makes this a minor scale. We are playing in G major, however, and the chord G major has the note B, not Bb. You can use the note B as well a Bb over a blues in G major. This will also work well over rock, country, jazz, funk, or whatever. If we look at this scale in a diagram form, you can see the minor 3rd Bb and the Major 3rd B. They are right next to each other. Again, we are going to use both of these notes. I find the note B by visualizing the triad G major laid over the top of this scale. The chord G Major contains the notes G, B, and D.

Here is a lick without the major 3rd. (listen to the lick)

Lick #2 uses the major 3rd. (listen to this lick)

Hear how the notes seem to have a brighter sound with the major 3rd? Using this device will open up your playing to new sounds. Once mastered, you will never go back to using only the minor pentatonic scale. Furthermore, some of the minor pentatonic notes played at the wrong time will no longer sound right to you. One word of caution; never use the major third over a song in a minor key, only songs in a major key. Now let's learn some more licks using the Major 3rd, in this case the note B. (listen to lick #3)

Now lick #4 (listen to this lick)

Now let's try lick #5 (listen to this lick)

Our sixth and final lick incorporates major 3rds and the blues scale. (listen to this lick)

These are just a few examples of licks using major thirds and the minor pentatonic scale. Try to fit these into your style of playing. You don't need to start them on the same beat every time. Try starting them whenever it feels right. Once mastered, change them and make them your own.