Planning begins with estimating and ends with scheduling. Long term scheduling won’t help you stay on task as well as short term planning. One method for this is The Pomodoro Technique. You can get some software to help you do the pomodoro technique.
Eliminating distractions has more to do with what you’re doing than with what others are doing. Checking email, answering the phone, instant messaging, social media, and internet browsing can typically be postponed.
There are some great tips in The 4-Hour Workweek
I also recommend that you try working from home or from a cafe near your office. It gets you away from the people who need your help, but can really wait, without completely isolating yourself.
Finally, keep track of what you spend your time on with Rescue Time.