Set time limits for all of your scheduled tasks. This ensures that you haven`t listed more than can possibly get done in a day (forcing you to leave at the end of the day feeling like you have failed to accomplish what you set out to do!) and let`s you `add in` tasks that will `fit`.
Have 10 unexpected minutes available? Add in a 5-8 minute task. Most activities expand to fill the time available. If you haven`t set boundaries you are likely to find your 10 minute task taking you the full 30 minutes you have open before your meeting.
Scheduling time limits for your tasks not only ensure that you are not OVER scheduling your day, but it also helps you keep on track for the tasks you do take on. You'll likely find that you accomplish more in a day simply by keeping loose track of how long you are spending on each task.