Learn to distinguish between interruptions.  Some are good, some are tolerable and some are avoidable.  A conscious act of judgement should govern your response.  Once you are interrupted, employ some damage-control hints, such as:

• Set a time limit and stick to it.  Say ‘I have 5 minutes – will that do or would you rather fix a time for later’?
• Set the stage in advance – you are very busy with a deadline in sight.
• With casual droppers-in, remain standing.  If they sit down, perch on the edge of your desk.
• Meet in the other person’s office – then you can determine when to leave.
• Avoid small talk when you are busy – it doubles the interruption time.
• Get the other person to the point.  Don’t be afraid to interupt the interrupter, asking them what the problem is.  What is the purpose of his or her call?
• Be ruthless with time but gracious with people.  Listen well.  Be firm but friendly and helpful.
• Have a clock available where visitors can see it, and don’t be afraid to glance at it a few times.  Explain about your next appointment, a white lie is better than a black interruption.