Whether you’re in a real, private office or some sort of cube or other open-office structure, you can set things up to encourage folks to communicate with you on a frequent basis. Or you can send a clear signal that you’d really rather not be bothered.
If you have a true office, look at your office door. Is its normal position open or closed? When you enter your office, do you automatically close the door behind you? You fail! Your office door is an outright signal to your troops. It doesn’t matter if you put a sign on it that says, “I’m always available! Enter!” Communication is going to be greatly diminished by that door.
Leave that door open virtually all the time. Yes: even when you’re working on a task that requires concentration, and you’d rather not be disturbed. It is more valuable to be disturbed by someone who has decided he wants to communicate with you. If you need privacy and concentration to get that big thingy done, come in early, stay late, or lock yourself in your study at home. The work office is a place for interaction with others, not privacy.
Of course, I’m not saying the door can never be closed. If you are holding a meeting and need the privacy, or if the meeting is making too much noise, then by all means close it up. In general, however, remember that your closed door is a barrier to success. Keep that barrier removed whenever possible.