I have just wrote a blog post on effective time management, yet I cannot post links at the moment. Basically it is all about being focused on the main tasks, and not getting distracted in the meantime, for me, the greatest sin is checking the social sites - I try to leave updating Twitter, Facebook etc. till the evening, as I know, that when I do it a number of times during a day, I end up browsing through those sites and loose 10-15 min each time - multiplied by number of times a day. So my first priority at the moment is to resist checking social sites, and get on with the tasks in hand.
Writing down what you plan to do during a day will help. Of course, business plan is a must, but don't forget to check it on a regular basis too!