The Flash 8 Best Practices document has been posted on the Developer Center. This is an updated version of the Flash MX 2004 Best Practices document that was out there, but doesn’t contain the ActionScript stuff (which is here instead: http://www.macromedia.com/devnet/flash/articles/as_bestpractices.html).
Most of this can be found somewhere in the documentation, but it wasn’t consolodated into a single place. Hopefully it will be in the future But for now, it’s here on the Developer Center:
And if you have things to add (there are always best practices to add), let me know and we’ll consider everything for a future revision!