1. Do a trial run a few days before the real interview, with a friend on the other end to give you feedback. Treat this trial run the same way you'll treat the real thing, including wearing the outfit you'll wear for the interview. Your friend can tell you if you're talking too loudly or not loudly enough, if the pattern in your shirt is playing oddly on camera, or if you're washing yourself out with overly bright lighting.
2. Pay attention to your physical background. You'll look much more professional sitting at a desk or table and against a neutral background without any clutter. Make sure that you don't have wine glasses, cigarettes, or clutter visible in the background.
3. Pay attention to the lighting. Aim light at yourself from the front, not from behind you. A lamp with diffused lighting about six feet in front of you works well. You can also try covering your light source with a cloth to soften it. And make sure that you're not backlit from a window or light source behind you; if you are, you can end up appearing on the screen as just a dark silhouette.
4. Keep other programs on your computer closed, especially if they might make noise during the call. You don't want a beep every time you receive a new email, for instance, or a reminder popping up of that other interview you have tomorrow.
5. Position yourself correctly. Don't sit as close to the computer as you normally would. Instead, sit a bit farther back so that your face and upper shoulders are framed in the shot. Additionally, place the computer slightly higher than you normally do, so that it's capturing you face-on and you're not looking down at it. (An easy way to do this is to simply prop it up on some books.)
6. Use the highest-speed Internet connection you can. On slower Internet connections, video may not align well with the audio and can cause awkward time lags, so use the fastest connection you can. If nothing else helps, try plugging your computer directly into your Internet cable, rather than using a wireless connection.
7. Remember to look into the camera, not at the picture. If you look directly at the image of your interviewer on your computer screen, you'll appear to be looking slightly away from her. Instead, looking directly into your webcam will read as direct eye contact on your interviewer's end.
8. If you find the image of yourself distracting, cover it. Skype, for instance, will include a small image of yourself in the corner of your screen. If you tend to watch the image of yourself rather than watching your interviewer, change your setting to remove that window altogether—or just cover it with a sticky note.
9. Plan for technological difficulties. Keep your computer plugged in so the battery doesn't die, and keep your phone on hand in case the interview mode changes at the last minute.
10. Don't hesitate to tell your interviewer up front that this is your first time doing a video interview. That will help break the ice, and most interviewers will be very understanding (and inclined to cut you some slack if you seem uncomfortable).
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager's Guide to Getting Results, and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.