(This post stems from my frustration of being interrupted at work.)
1. Respect that they are in the middle of doing something
Some people seem to think that other people should drop everything that they are doing once they come calling.
I can't count the number of times I have been interrupted in the middle of typing code, or an e-mail, or an instant message (read: IM) to someone. You know how it is when you drop your train of thought; later you have to try and get it back, and it's not always easy!
There are so many reasons why you shouldn't interrupt someone and demand their full attention immediately. Even microprocessors need to do something called "saving context" before handling an interrupt. This allows them to restore the context after handling the higher priority task at hand, and continue whatever they were doing before that.
I have been interrupted while reading an e-mail, and then forgot to finish reading it (the e-mail had been automatically marked as read, and I didn't recall until later that I had only read it halfway). I have been interrupted while writing a piece of code, and then had to search again for the variable or function that I was going to use (for non-programmers, consider that a word I wanted to use). I have been interrupted while typing an instant message to someone, and sometimes that is the worst, because unlike an e-mail where you write everything fully before you send it out, in IM you will write short sentences and send them one by one. If you were going to write three sentences, and you are interrupted after sending the second one, then the third sentence which may serve as a clarification of the first two sentences is gone. While you are handling your interruption, the recipient of your IM might read your two messages and not be able to make head or tail out of it.
After being interrupted numerous times, I printed out a notice saying something like "Please give me 60 seconds to save my context before interruption" and stuck it around my cubicle. (I actually printed out three, because there was no perfect place to put one) I don't think more than five people have noticed the paper that I stuck up. A few times, I had to gesture to it when people came to interrupt me, just so that they would allow me my 60 seconds.
That is not to say that I always need 60 seconds, of course. If I can "save my context" in less time, of course I could give my attention to you sooner. And if I need more time... well, I don't believe that it is not possible to at least stop for a while just to let a person tell you what they need, even if you are rushing for a deadline. As long as you get to save your context first...
2. Respect that they might have more urgent things to do at that moment
Like I said in the first point, someone might not be able to give you their attention immediately, but I feel that 60 seconds is enough time to stop what they are doing momentarily just so that you can tell them why you came looking for them. But depending on what you need from them, what they were doing might actually be more important/urgent.
So it is okay for them to tell you that they will come back to you later. It is okay for them to do so, and it is okay for you to tell people that you will get back to them. It works both ways, if the person being interrupted is busy, they can ask, "Can't this wait?"
3. Respect their working hours
We need to understand that our colleagues might want to go home at the end of the day, even if we are staying late.
This has happened to me so many times. Sometimes I am staying late just to finish up something, and hoping that I can finish quickly and then go home... but then someone sees me there and assumes that they can come and have a lengthy discussion with me. :(
This happens especially in a flexi-hour working environment, because some people come in late and stay late. So even if you came early, as long as you are still in the office, you become "fair game" for people to come looking for you. And who would want to come and talk to you about banal things but these people who are staying late because their working hours hasn't ended? That is not to say that it does not happen when there are fixed working hours... after all, no one chases you out of the office after working hours, right?
That is why, when I go and talk to someone after 6pm, I will try to ask whether they have time or whether they are going home soon. If I know that a person usually leaves earlier than that, at 5 or 5:30, then I would do the same around that time.
Unless if the matter at hand is super-urgent, of course. That is always a reason to interrupt someone no matter what they are doing. But we need to compare the urgency of what is interrupting and what is being interrupted, don't we? Like preemption on Tetra radios... heh. (work-related analogy)
Actually, this works for everyone. Not caring what rank you are, you need to show some respect for the people you are working with. It is hard for me to tell off managers for interrupting me, though... :P