When diving with other team divers I'll do the bubble check, mod-s, SADDDD sequence (GUE EDGE for GUE divers) and plan the dive. Because I tend to take a class about every 6 months I get plenty of time to practice certain skills (toxing diver, unconscious diver, OOG, any of the 9 valve failures, failed primary light, and maskless). As a UTD Divemaster I get ample oppurtunity to practice when assisting classes, demonstrating, or helping people prepare (or preparing myself) for upcoming training sessions. My dives tend to be fun, however. So what usually happens is we'll throw something in here or there on a dive but it's never the focus of a dive.
When diving with divers who aren't trained in like manner then I tend not to practice anything as they have no interest in it or often don't understand it when I do -- the training protocol is can sometimes be drastically different than what they are accustomed to. Many of the purely recreational divers that I dive with, however, don't ever practice anything.