The best way to get the most out of your day is to take your time seriously.  I’ve already talked about the importance of tracking your time and reducing the time-thievery of meetings, but here are some additional things that I have found help me to maximize the time in a day.

• Keep a to-do list.  There are three key elements to this.  First, capture everything that needs attention so that nothing slips between the cracks.  Second, scope the tasks; a rough ballpark will do.  Third, prioritize.  It’s fine to pick one or two small tasks to cherry-pick and get done, but if you’re breaking your own prioritization regularly, you need to dig into why you’re avoiding the bigger tasks.  I always re-visit my to-do list first thing in the morning (often a good time to scrap the old version and re-write a cleaner one) and last thing at night, with periodic updates as needed throughout the day.  This helps tremendously with focus, as well as providing a sense of accomplishment for abstract work; it always feels good to look at a list of crossed-off items at the end of a day.
• Attack e-mail strategically. It’s easy to get constantly interrupted by e-mail, just like it’s easy to let meetings take over your life, particularly if you are intersecting with multiple teams and leading a project.  A lot of times, being responsive to issues raised in e-mail is a key part of leadership.  However, this does not mean you are doomed.  I do a thorough clean-up of my e-mail first thing in the morning and last thing at night (funny that), and in between, I do a lot of sorting.  Items that need a response stay in the inbox; everything else gets deleted or filed into an appropriate folder.  This means that anything in my inbox needs attention; when I have a few free minutes between other tasks, I try to knock a few of these off.  Staying diligent about this process can be challenging, but over time, it becomes a habit, and that’s powerful.
• Work your calendar.  This is a life-saver, particularly when you’re constantly overbooked.  Every meeting goes into my calendar, no matter how short.  If I can see it coming, I document it.  Every event in the calendar also has an appropriate reminder warning; usually, this is 15 minutes for meetings, but it can be 12 hours or more for events I need to prepare for the day before.  Again, you need to do this for a while until it becomes a habit; once you hit that point, all of those mental cycles you spent reminding yourself that something is coming up or that you need to prepare for something can be reclaimed.  Your brain is free to work on other things.  Pro-tip: when you’ve got something you really need uninterrupted time to work on, book time for it in your calendar.  If you’ve trained your team to look for conflicts when scheduling, this is very effective.  You can also put reminders into your calendar (set as not busy) to follow up on various issues or commitments from the team.  If you are diligent about working your calendar, you can see at a glance in the morning how much time you’re going to have to devote to that to-do list.
• Clean your desk at the end of the day. It doesn’t have to be spotless; nor do you need the perfect organizing system.  Just clear some space.  Make sure the things that need attention are somewhere you can put hand to them easily, trash and recycle the things you don’t need anymore.  Not only does this help prevent things from going missing, it also has a psychological benefit.  Clutter builds up over time, and when you approach a cluttered environment, it can feel overwhelming.  If you clean/straighten your desk at the end of every day, it’s going to be that much easier to engage the next morning.
• Take regular breaks.  If you’ve been working on something for two hours or more, you need to take a break.  You don’t need to go far; you don’t need to start doing something else.  You do need to stand up, walk around a little bit, get the blood flowing, and allow your unconscious mind to take over the problem-solving for a little while.  Some people like quick naps (doesn’t work for me), others do a lap around the building.  Do whatever works for you.
• Disconnect when you need to. Nowadays, we’ve got IM, Twitter, and Facebook to deal with in addition to e-mail.  It’s okay to log out.  Really, it is.  When you really need to focus, clear all the potential distractions out of the way.  It can even help to have a separate workspace you can go to where people are less likely to interrupt and you don’t have all of your communication channels open.

Personally, I like to be slightly over-booked at all times.  This keeps the right amount of tension in my day such that I am constantly pushing to do more, so a lot of these tips are biased towards dealing with being over-booked.  What works for me may not work for you.  The important thing is to make yourself consciously aware of what is affecting your time use and productivity.  Track and measure your own successes and failures, and you can customize your workflow to get the most out of every day.