Fix a date and decide how often you want to have your salon (monthly, bi-monthly, quarterly).
Fix a venue. Don't worry at first about anything too fancy. It should be accessible and accommodate the number of expected guests.
Form an organizing team. This is crucial. Don't do everything on your own. Plus it's more fun working together. Involve participants in the decision making, and have at least couple of planning meets.
Aim to invite diverse people to the Salon who love the idea of sharing. Some good suggestions are Wikipedians, musicians, open source programmers, artists, DJs, teachers. Ask them to demo or talk about their work and how CC (or sharing) has helped them and the community.
Free is good but if you are having trouble raising sponsorship, don't hesitate to fix a door charge. A little cover charge will easily take care of refreshments and miscellaneous expenses.