I've conducted hundreds of phone interviews, more than i'd like to count. here's some advice i'd like to pass along, some of it (most of it) is pretty common sense, but i still get these mistakes. please feel free to add to the list, i'm sure i've missed some.
-usually I call the intern/job applicant, but if you're calling me, CALL ON TIME. if the call is 11am, 11:00-11:03 is fine. anything beyond that is pushing it. 11:15? don't even bother unless you have a really good excuse
-I can't stress this enough, get your time zones right, you already know i'm in et, if we agree on 12:30, know that I mean my timezone, not yours (i always try to write et after the scheduled time, but once in awhile I still get kids in pt asleep when i call with the attitude that I f'd up the call time)
-be somewhere quiet, VERY quiet. if you're driving / at a loud cafe / have friends yelling in background = dinged
-just like any other interview, don't be awkward, TREAT IT LIKE A FRIENDLY FORMAL CONVERSATION. since this is all voice I can't your body language, so instead everything will be judged by your conversation skills, tone of voice, confidence, knowledge etc.
-if the interviewer doesnt answer the phone, please know how to leave a formal/proper voicemail (name / your # / best time to get back to you / etc)
-common problem with phone interviews is both people speaking at the same time (especiallywith conference calls), if this happens, pause, and allow the interviewer to proceed
Specific to Skype calls:
-if you're calling from skype and i'm on my cell (ie with international calls), PLEASE have a clean connection. I understand if the call drops once, more than that it becomes an annoyance.
-if we're both talking on skype assume it's NOT going to be on video unless I say so beforehand, so don't load your webcam when I call you. everyone is different so if you're not sure feel free to ask your interviewer beforehand if the call will be on video
-don't have an unprofessional avatar / username (i've seen some weird ones...)