A simple way to get more done during your day is to do your most important tasks during your productive hours.  Some people find that they're more productive in the morning.  Others are more productive at night.  And some are more productive in the afternoon.

If your schedule allows it, you could take it further by only working during your productive hours and taking the rest of the day off.  For instance, if you find that you get drowsy in the afternoon, you can do your work in the mornings and evenings.  And you can take the afternoons off.

Another example is if you do writing.  You might find that you're more creative during certain times of the day.  If you're more creative in the morning, you can do the bulk of your writing in the morning.  The rest of the day can be left for your routine tasks.

To figure out which hours you are most productive, try keeping a time log.  Record every activity you do during your day and the time you start each activity.  Then see which hours you spent working and which hours you didn't do any work (such as surfing the web or chatting with co-workers).

Keep a time log for a week.  You might see a pattern of which hours you spend working.  Those hours may be your productive hours.

Also, note how you feel during the day.  Are there hours where you feel more energized?  When you're energized, you tend to be more productive.  Also note which hours you're more alert.  See if there is a period where you feel drowsy.  Perhaps you're drowsy after lunch.

Once you've figured out which hours you're most productive, do your more important tasks during those hours.  Or move more of your workload to your productive hours.  And do less work or easier tasks during your non-productive hours.