Smart hiring managers know to use a phone screen to screen in appropriate candidates and screen out unsuitable candidates. And they know that before you start the phone screen, you verify this is still a good time to call.
But what if you call the candidate and he or she answers the phone? Can you just start the screen? Nope. This is probably the first time the candidate has heard about your interest, and most people are not ready to talk. If you are phone screening a big-time extrovert (like me 🙂 it could be fine. But many technical people are not flaming extroverts, and need to think about their answers a bit before answering. Some candidates want to research your company, now that they know you’re interested. Even more importantly, you send a specific message when you schedule a phone screen: that you respect the other person’s time and you want to make sure the candidate is ready to talk.
As a hiring manager, you are in the position of power in the interview. You can use that power, or abuse it. When you tell a candidate, “Let’s talk now,” you’re telling the candidate his or her time is not valuable compared to yours. From your perspective, you may be right. But from the candidate’s perspective, you’re wrong. If you treat your employees with respect, why not treat your candidates with respect too? Remember, candidates will think that the way you treat them is the way you treat your employees.
If you really don’t have much time, you can say, “I’m on a short leash, and I can phone screen you now or in two days at such-and-such a time. What works best for you?” When you explain why you want to phone screen immediately without scheduling, you’ve involved the candidate in the problem-solving, and are acting with respect.
It’s possible to schedule phone screens right away — but ask. It’s better for both you and the candidate to schedule slightly farther out in the day, so that both of you are relaxed and prepared.