To get good quality on a skype interview:
1. Uncomfortably hot lighting, eg two bright anglepoises close to you - if during the day, use a bright window, and the anglepoises. Really! You need as much light as possible!
2. External microphone - video mike, singing mike, karaoke mike, external computer mic. Preferably not a mobile phone mike, but this would be better than the computer's built in mike.
3. Your head in the picture must not have too much headroom (a large gap between you and the top of frame - rule is top of the head on the top of the frame - think how a photo portrait is framed).
4. If your camera is external to the computer, make sure it is placed just above the computer screen (this helps a lot with eyelines).
5. Set your mic recording volume to 75% (3/4).
On windows you do this by: .....
On Mac you do this by: ......
On Ubuntu you do this by going to System - Preferences - Sound - Input, and set to 75%