Do a google search for 3-point lighting. Setting up 3-point lighting will make your models look great and does not have to cost alot either.
Also, alot of people forget the audio portion. Don't forget the Audio!! Try to use some decent quality mics that are as close to your chat models as possible. "Dampen" your studio as much as possible to absorb as much echo as possible.
Software wise, you are limited to what each site offers you. To get the best performance though, use a very fast computer. With our own
LiveCamNetwork for example, the faster your computer is, the larger the picture, the higher the frame rate, and the higher the bitrate you can stream at. If you bought an expensive camera, don't skimp out on the broadcast computer.