We know that if you stand up for just one or two minutes every hour, it can reduce the negative effect of sitting all day. Technically, you don't even have to move, the act of standing alone helps. When you're in the moment and working hard, it's difficult to remember. I found enabling the hourly announcement in OS X the best reminder. To set this, click Settings > Date & Time > Announce the time. Windows users can set up a similar hourly reminder as a task by clicking Control Panel > Administrative Tools > Task Scheduler.