As a professional, "please" and "thank you" are still important (as is "I'm sorry," which Lily Herman explains beautifully here). However, they aren't the only words that can help you navigate through a tricky professional situation. I learned the following phrases from a previous boss, and have been using them ever since.
"In the interest of..."
So, when you're responsible for running an interview, you need a diplomatic way to cut people off. "It's time to move on..." or "That's all the time we have..." feel a bit harsh, like you've decided the other person is no longer worth listening to and are readying the orchestra to play him or her off of the stage.
When dealing with a long-winded person, my former boss suggested that I use the phrase "in the interest of time." For example: "In the interest of time, we'll need to move to the next question." It's a short, yet mighty phrase. You no longer appear to be arbitrarily deciding that another person is boring or that his turn is finished. You're reminding everyone involved that interviews only last so long; and thus, to cover the requisite ground, moving on would be advisable.
Rather than feeling cut off, the other person feels like a valued participant--one you're letting in on the parameters of the interview, so that he or she can play a part in the exchange running smoothly. (Bonus: This phrase also works for meetings and the Q & A portion of presentations.)
Check out the rest of this article (including another valuable phrase) on LinkedIn.