Plenty of advice is available for standard interviews, should phone/Skype interviews be approached any differently?
(This was asked on twitter by @emilyandthelime, I have my own, partial answer that I'll post)
A major difference from an in-person interview is that interpersonal visual cues such as eye contact are absent or impoverished (even in Skype, because of poorer resolution / latency / smoothness than actual reality) and a rapid verbal back-and-forth is usually impossible. So it's more difficult to assess the interviewers' reaction and when they've had enough of your answer.
Typically the interviewer(s) want to hear you talk about your research for several minutes and will ask a few rather open-ended questions that are mainly designed to get you talking. You should run with that and just keep talking and let the interviewer(s) say something when they want you to stop- it's too difficult to try to monitor their nonverbal reactions. Some candidates make the mistake of not saying much, in an attempt to not over-sell themselves or in an attempt to act suitably subordinate. The interviewer(s) really want to hear you describe your work in your own words and feel your enthusiasm and general attitude.
The interviewers themselves will realize that it's difficult to have a normal conversation rapport so don't let any awkward moments or technical difficulties stress you out, the main risk is that you won't say enough.
To show you aren't off in your own world, you can't use the normal nonverbal skills very much, therefore be paticularly sensitive to the exact questions they ask, but once you answer the specific question feel free to answer more broadly, a broad perspective tends to impress.