being relatively inexperienced in the bach style, my general tendency is to avoid dissonances like perfect 4ths or 7ths on any downbeat. I was a little surprised to discover that bach actually does this kind of thing all the time, but he resolves these dissonances into imperfect consonances (6ths or 3rds). so for example if he has a D quarter note in the bass, and a C eighth note melody, he’ll move that note to Bb in the next eighth. this opens up a lot more possibilities in terms of writing, as these dissonances are often a pain to avoid, especially in cadences.

another “rule” in the way bach resolves dissonance is that if he uses a dissonance, any note that can be resolved by a half step, should be. this means that in two voice writing, if you have C and F, the F should be resolved to E. for B and F, B goes to C and F to E. always resolve by half step if possible.