Here's a good excercise, grab any chord you feel real comfortable with. Now just strum down playing to the 1/4 note counting 1 2 3 4 1 2 3 4 etc, put a little extra emphasis on the strum that falls on the downbeat of 1. Now do the same but slightly change it by throwing in an 8th note rhyhtm on beat 3...so you'll have 1 2 3 & 4 1 2 3 & 4. Keep adding to it, 1 2 3 & 4 &, then 1 & 2 3& 4&.
Once you feel comfortable with that try playing syncopations.
ex: 1 (2) + 3 + (4) the beats in parenthesis are not played. Doing stuff like this will help you out. Also try getting together with just a drummer sometime.
