I started writing a table:

  start_time, end_time, activity, project
  08:00, 08:30, emails,
  08:00, 08:35, facebook, procrastination
  08:35: 09:00, work, project1
  09:00: 09:30, hackernews, procrastination

It helped me tremendously to reduce the amount of wasted time. The key is to be absolutely, brutally honest in this table.