In an interruption-driven culture, it's too easy to let everyone else decide where your attention goes and how to spend your next 10 minutes. If you jump every time your phone rings, a new email arrives, your Blackberry buzzes, or someone stops by your desk, you're undermining your most important work and costing your company money. A recent study shows that unnecessary interruptions costs the U.S. economy $650 billion dollars in lost productivity per year.

Being available to your boss and co-workers is part of your job. But the most creative and important work you do requires total focus and attention for an extended period of time. Your brain needs at least 15 minutes of uninterrupted time to dive in, concentrate on one thing, and get into the zone where you're truly focused and doing your best work. Time blocking is a technique that sets the stage for that to happen.

When you've got a project that requires deep thinking, block out hour-long "meetings" with yourself to devote your full attention to it. During your time block, forward the phone to voicemail, shut down Microsoft Outlook, silence your Blackberry, and if you have to, leave your desk with the materials you need and focus solely on the task at hand. Sound crazy? Even an employee low on the totem pole can do it.

I used to work as a software programmer at a busy office that had an open seating layout. There were no cubicles--sales people sat elbow to elbow next to graphic designers who sat next to engineers, and people constantly interrupted each other. It got so bad that when I was on deadline, I'd book hour-long meetings in a conference room where I was the only attendee. I'd put the meeting in my calendar a day or two ahead of time so that I showed up as "busy" in Outlook. When the time came, I'd steal off to the conference room with my laptop to work uninterrupted. When I confessed to another programmer that I was holding fake meetings with myself just to get work done, he asked if he could join me--under the condition that we would not distract one another. I got the most work done in the shortest amount of time during those blocks.

Time blocking works best when you've got a discrete, single task or project that involves deep engagement, like research, number crunching, brainstorming, or writing. Set a definite start and end time when you don't have other meetings to attend. Commit to coming out of a single time block with a specific task accomplished. If the Internet is too tempting a distraction, download the files you need to get the job done before you start, and turn off your laptop's Internet connection during your block.

When you work in an office where interruptions are the rule and not the exception, use time blocking to reclaim hours you'd otherwise spend dealing with distractions.

Gina Trapani is the author of Upgrade Your Life and founding editor of Lifehacker.com. Work Smart appears every week on FastCompany.com.