Prioritize around your Most Important Tasks
Trying to plan ahead every minute may seem like the way to go at first. However, we sometimes forget that any plan needs space for the unexpected. Not only for big or complex projects, but also when just planning for the day.
That's one of the reasons why it's best to define the most important tasks for the day (or MITs) up front. When an unexpected event knocks on the door, we know that we need to reorganize our schedule to protect the MITs.