I have done this a few times and find it annoying, but increasingly search committees and recruiters want to Skype. The last time I did it was for a job at the University of Hawaii. Obviously, they want to screen people before going to the expense of flying you in from the mainland. As has been suggested, you need to dress fully for the interview; how you dress though depends on your industry. Some things to consider:
• where will you do this? At home? Work? Or some other designated area? You need to think about this for a couple reasons. Be certain that your location is free from distracting background noises (coworkers, street traffic, a barking dog, kids, etc). You need to be in a perfectly quite space so that your voice is the only sound they will hear.
• What will be behind you while you are on camera? You should have a nondescript background (like a blank wall or a bookcase of innocuous books) because they will see and notice whatever is behind you. Having the wrong thing in the background can make a very bad impression.
• If you are at home or work, experiment beforehand with lighting so you have a good sense of how you appear on camera. Bad lighting has the potential to reflect poorly on you so look into this. You may want to use some sort of spotlight so that you are not too dark.
