1. Generalize the note values and rhythm-types (dotted values, triplets, etc.) used in one voice, and make sure they are used in the other.
2. Reduce, re-use, recycle: distinctive rhythmic cells should not be too great in number or too various. Re-use and recycle them in the second voice if they occur in the first.
3. Pay attention to other aspects of style and make sure the voices don’t contradict – (but this guideline is 90% accomplished simply by maintaining clear harmonic and melodic progression as per the well-formedness guidelines!)