It's not that hard, really. If you memorize your presentation you can reliably get within a few seconds. Most of the transitions don't require pinpoint timing a

It's not that hard, really. If you memorize your presentation you can reliably get within a few seconds. Most of the transitions don't require pinpoint timing accuracy, anyway. It's really common to overlook the amount of time that will be eaten up by applause/laughter, though. Don't forget to give yourself some breathing room for that sort of thing, particularly if your speaking format penalizes you in some fashion for going over time.