To play a fifth, play a note with your first or second finger on any string except the first string. Then, play a note one string up and two frets higher using your third or fourth finger. For example, you could play the seventh fret of the second string (an A) with your first finger and the ninth fret of the first string (an E) with your fourth finger. This hand shape is called a "fifth shape." Remember it, because it is an excellent default when making up a bass part.

Another way to play a fifth is to play the root note with your fourth finger on the third or fourth string, and then play the higher note with your first finger two strings higher and three frets lower. This method is a little more awkward, but sometimes useful.

A fifth has a very hollow, tight harmony. Play a fifth and try to remember the sound of it. Another good way to get the sound in your head is to think of the first notes in "Twinkle Twinkle Little Star."

Fifths are very useful for bass lines. If you don't know what to play for a chord, just put your first finger on the root note (preferably on the third or fourth string) and use a fifth shape. The two notes of the fifth are both chord tones, and will sound good in a bass line.