So you've sent out resumes, and finally you get a bite: someone wants you to call to schedule an interview.
Have your calendar ready beforehand. Don't begin the call without an idea of what time would work for the interview. However, the hiring manager usually suggests a time first, since they are busy and do not have to interview you. Thus, be as flexible as possible, since you're trying to make a good impression.
(Most of the time, they will call you rather than you call them. In this case, make sure to have a general idea of your schedule when you're job hunting so you can answer these calls. If they call at a bad time, you can politely say that you don't have your calendar at hand and will call them back as soon as possible. Then call them back AS SOON AS POSSIBLE with your calendar ready.
If they don't state a time immediately, be ready to suggest a couple times that would be convenient for you. However, if you suggest a time, don't decide later that it would be a bad time. You're stuck with that time.
When a time really does not work, say that you have other commitments and leave it at that. Don't go into any further explanation unless it would be obvious to everyone that it is more important, such as a doctor's appointment. And don't start explaining why you have to go to the doctor, they don't need the details.
If you know that you really do better in the afternoon, go ahead and try to steer the conversation toward that time, saying that afternoons are really more convenient. But don't say that you're sleeping in past 1 PM!
Above all, be professional. Whenever you're on the phone with a potential employer, be sure to pay attention to what they're saying and present yourself well. Focus on being articulate and polite.
Although you could ignore all of these guidelines to test how much they really want you and are willing to go through to get you on their team, I wouldn't recommend it.
Update: Video uploaded!