Determine if it is important and urgent and needs your immediate attention. If it does not, set up an appointment to meet with them. Alternatively, establish a door policy. If your door is open, you are available to your staff. If you use this system and are sparing with the use of the sign, staff will generally respect your privacy.
Phone calls are sometimes more demanding than people.
Train yourself to let your phone roll over to voice mail. On your message, remind people to be very specific about why they are calling so that when you return their call, you can provide them with the information they are seeking. That way, even if they are unavailable, you can leave them a message with the information they need, thereby breaking the dreaded phone tag loop. Return the courtesy. When you leave a message, be very specific about why you are calling.