What are the rules of keeping rhythm on guitar?

Answer 1

The most important thing to keeping rhythm is never to get off beat; use your drummer and keep your hand motion constant. You need to be able to play constant eighths, quarters, sixteenths, eighth and sixteenth triplets, and swing if you want to be able to play a variety of music.

You also need to be able to play the chords right; this doesn't just mean hitting the notes, but doing it fluidly, striking muted strings when you need to, moving between chords smoothly, and so on. If you're selecting your own chords rather than using a certain progression, make sure to "color" the chords to a certain feel; use one chord primarily, keep all of them in a key, and only transition between major, minor, and seventh when it sounds right.

If you're able to play the chords you need to in the time you need to, you'll be alright, but in order to keep the rhythm interesting try to know a variety of ways of playing every chord; this way you can substitute them whenever you like, and it will fit the sound of the song while changing it. Once you're able to do this, you can experiment with more complex times or chords, but the basics will all be there.