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. Really! You need as much light as possible!
2. External microphone - singing mike, karaoke mike. Preferably not a mobile phone mike, but this would be better than the computer's own 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).