You're familiar with those weeks where the universe conspires to dump every possible commitment on you at once, right? I am finishing one, and would very much like to see it end. Today's ballroom tip will therefore be to the point, despite being the habit that makes the biggest difference in the productivity of my practices.
Plan practice in advance. I like to agree with my partner beforehand what dances we want to work on and how we want to work on them. We make notes at the end of practice what needs to be checked or revisited next time. Each of us gets to select figures or elements that bug us, so our pet peeves get equal time. This helps avoid discussions of what we should work on that devolve into other topics far too often.
Our most productive practices start with 15-30 minutes of warming up, including some stretching, basic elements, and doing boxes or basic figures together. We then move onto our selected figures in the selected dance, dancing each several times to fix things. We finish by dancing through our entire choreography for that dance once or twice, to check how permanent our fixes were and how more global goals such as musicality are progressing. That normally takes about 45 minutes, so if time allows, we move onto another dance and repeat the procedure. We might finish with a full run-through if a competition is coming, we haven't worked on a dance in a while, or we want to check how all the dances stand. My practices that have followed this pattern are the ones with the most dancing, the most progress, and the least time spent discussing or arguing. I leave feeling like things have been accomplished. I hope it helps you as well.