All of the examples you have so far played involved a downward strumming motion which can be indicated by a t. With eighth notes there are two possible ways to play the previous rhythm. Sometimes it sounds best to use all downstrokes of the pick, and other times the technique of down and up (y) strumming is used.
This is called alternate strumming, and it is essential for the development of speed and accuracy.
Alternate strumming motion - tytytyty
When using alternate strumming on eighth note rhythms, use a down strum on the beat (the number count) and an up strum off the beat (the 'and' count). Apply alternate strumming to the previous example. As a general rule play eighth notes using alternate strumming, although some grooves work better with all downstrokes.
Many rhythm patterns contain both quarter notes and eighth notes. In this situation you can play all the quarter notes with down strums and alternate the strumming for the eighth notes, as shown in the following example. When playing this style it is a good idea to keep up the alternating strumming motion even when there is no up strum in the music. Instead, strum in the air just above the strings. This helps you keep time and keep the momentum of the rhythm you are playing.
Eighth notes can be very effective when combined with rests. In rhythm guitar playing the most important thing is where in the bar you place your notes and how they interact with the parts being played by other musicians. The following example uses the F7 chord, along with C7 and G7. These are chords I IV and V in the key of C. Once you are comfortable with this example, try playing a 12 Bar Blues using these chords.
A dot written after a quarter note means that you hold the note for one and a half beats.
A dotted quarter note is often followed by an eighth note.
This example demonstrates the use of the dotted quarter note. Remember to tap your foot on each beat and count out loud as you play. It is also important to use your metronome with everything you practice.