• I think the best thing to do is to discuss the idea, the rules and the track (if there is a track) with friends long before - so there won't be big changes after the "official announcement". And "make sure" that others also like the idea behind your race. And wait a little bit for a good starting point. You might want not to start your race very near (in room and time) to a popular one (=already took place in the year before or so).
• A web page should be designed before and published with the "official announcement" IMO, so that everything can be read at one place.
• Over think how to update the web pages if the race will go on for weeks or months - are you willing to do it? Remeber that even in July 2004 not all participants of the Canonballrun 2003 have reached the goal but have IMO a right to be tracked on the official website...
• If you gather the TBs to set lose in a cache or event or ... create a puppet account so your own statistics keep right.
• Automatic update: The perfect idea IMO is what brad.32 suggested to me before the start of the "Rund um Deutschland 2004"-race: Use the watchlist-eMails.
• Give enough time for registration. Geocaching is an international game so give also Geocachers from another continent enough time to make racers ready and brought into starting position.

Send out updates to the people with a little info about what happened during the week. I make them funny, so people get a chuckle.

I also have little contests to win free tb tags as well. For example, I had a contest to see who can guess the bug that will put us over the 30,000 mile mark. and the winner was to receive a free tbug. Little things to appeal to the masses, I say.