Mine has 10 minutes between clients, so she probably looks at her notes from the week before to refresh her memory. If I were a therapist, I'd also get to the office early and look over the day's schedule to orient myself. Their memories aren't going to be perfect anyway, but the decent ones will at least make an effort to prepare, I think.

For those with literally no time between sessions? It's hard to imagine how they make that shift. I wouldn't want one who had such a tight schedule.