Watch the Rhythm Guitar Advice online guitar lesson by Allen Hinds from Melodic Improv
Playing rhythm guitar is like an art form. Like a poem or song that's several measures long, most rhythm guitar parts have a form to them.
When I started doing sessions in Los Angeles, I would play a different lick on every measure. It was an issue to the artist who knew what their song was supposed to sound like, so I learned that rhythm has a certain order to it. It might be three measures of the same pattern, and on the fourth measure you do a little turnaround or lick. You have to stay out of everyone else's way, too - don't step on the singer's toes. If you can play rhythm guitar, you can work! Everyone wants a great rhythm guitarist.