The easiest way with 4/4 time is a bass/strum/bass/strum. 3/4 time would be bass/strum/strum. Bass refers to the bass note in the chord, plucking the bass note for 1 count, then strumming the whole chord for a 2 count, and so on. So a measure of 4/4 measure of a G chord would be: bass note / whole chord/ bass note/ whole chord. Practice it with a metronome, and you will hear a definite rhythm pattern for each measure you play, and you will train your ears for good rhythm. Some refer to this as "bluegrass strumming", though much bluegrass involves alternating the bass note in the chord.