I once saw (via video podcast) a wise man (Jason Calacanis) say "starting is easy; finishing is hard." When he said that, it was a moment of absolute clarity for me. I'm not saying he verbalized the meaning of life. He did state, however, what I've often conceptualized but was never able to verbalize.
What Jason stated in 6 words is what I've seen many colleagues struggle with. Who doesn't have projects and tasks to complete and deadlines to meet? I've tried multitasking, thinking it would make me more efficient. I've tried using a productivity pyramid. All I did was start more tasks, not finish more. That's the key right there. It doesn't matter how many things you start if you never finish them.
The solution to my past problems has been the use of kanbans, referring to them as information radiators. These information radiators were large billboards strategically placed around the office so anyone could passively see the status of the current project. You could see what the highest priority was, what was currently being completed, and what was being delayed.
I believe the key to those successes was in the ability to visualize our work. Everyone knew exactly what they needed to complete and everyone else knew if it was getting done. People were not allowed to go on to ancillary activities until their assigned tasks were completed. Another important facet of the kanban, we limited our work-in-progress. This forced-focus on limited tasks and constant feedback loop is very powerful and very productive.