In a bar of sixteenth notes in 44 time, there are 16 different positions for notes within the bar. The first beat is 1, the second note of the first group of four is called the "e of one" the third note of the first group is called the "and of one", and the fourth note of the first group is called the "a of one". As with other subdivisions of the beat, the system then continues through the bar - 2, e of 2, and of 2, a of 2, etc.
As with triplets and eighth notes, a good way to master the use of 16th notes is to strum constant 16ths with the right hand and select which part of the beat will sound by pressing down with the left hand. The other parts of each beat should be sounded as percussive strums. Here are some exercises using this technique. Be sure to use your metronome, count out loud and tap your foot on the beat without any hesitating or extra taps between beats.
E7
Percussive strumming can add a lot to the feel of the music you are playing. It is often used where there are rests in the music, particularly with 16th note rhythms. Here are two examples. The first one uses 16th notes and rests, while the second one replaces the rests with percussive strumming.
The following example uses a thirteenth chord (E13), which is an extension of the E9 chord. It is achieved by forming the 9th chord and then placing the 4th finger two frets up the neck on the first string. This chord is shown in the chord diagram above the notation, next to the E13 chord symbol.
E9
E13
E7
In this example the percussive strums are all eighth notes. Experiment with these chords and percussive strumming to create some of your own rhythm parts.