At each Swancon, there are a few things traditionally done by the next year's Swancon. None of these things are cast in stone: you can negotiate with the appropriate committee to change them if you so desire.
You will generally have a launch event at the end of the second-last day of the previous Swancon. Your launch may involve a video and/or performance, may involve the release of a Progress Report, and may announce venue, guests, and prices. Launches are generally well attended.
It is traditional for next year's committee to run the convention registration desk from the end of their launch event until the end of the convention. This gives you a small taste of what you've just let yourselves in for, and takes some weight off the current committeee. It is expected that you will sell memberships to your convention from the registration desk. If you plan to sell T-shirts, it's probably worth letting the previous Swancon know this as early as possible so they can adjust downwards the number of T-shirts they are planning to order for their own T-shirt sales.
Art show and Auction proceeds
It is traditional that this year's convention, if they run at a surplus, gives half the profits from the auction and art show auction to next year's Swancon. Remember that Swancon generally takes 10% of each auction sale, so you can expect 5% of the auction receipts. If the previous Swancon is strapped for cash, you might choose not to accept this money.