I struggle to correct as little as possible. Sometimes it is difficult: beginners have expectations and people get frustrated when they don't know why something isn't working.
I try to make sure that any verbal corrections I am unable to avoid do not interrupt the flow of training. This means that I keep my comments quite brief (often a word or two does wonders), and simple enough that they can be heard and processed while we are both moving. I try to make it very easy to ignore whatever comment I make, if my partner is not interested or has their own agenda. Nothing I have to say could be so vitally important that it should be forced on the my partner.