I have Premiere CS3. I made an 18 minute video for a company. They want a Flash version for their website and I have no experience in this area. The manual just says to choose one, and the Classroom in a Book uses the example of NTSC 512 kbps. I don't know which one to use or why. Any advice would be appreciated.
The choice will depend on the file size (for download speed, basically), that their (your clients') site requires. You might have to ask their Webmaster what he/she wants/requires. The quality will likely be better, if you choose the fastest connection preset, but that might not work on the design of the specific site, and the file size will very likely be larger.
It's like doing output for print advertising - one has to call the printer and ask for specifics. Any good Webmaster will be glad to instruct you as to their specific requirements.