I’m not sure if this is what you had in mind, but these are a few things that come to mind right now in terms of web usability in general:
–Target Audience: For example, Flash is great for eye candy and stunning visual effects, but not great if the user is purely looking for information yet has to go through an intro and numerous special effects.
–Good Choices: A little Flash goes a long way. Flash is great for enhancing a static HTML site. You don’t have to make your whole site in Flash.
–Navigation: A cool Navigation bar is…cool, but again, think about your target audience. If it’s cool to look at, but hard to navigate, then it sort of defeats the purpose! Your navigation/menu bar is to help people navigate through your site, how ironic if you need directions to tell people how to use your menu bar. =)
–Text: try to use sans-serif text for easy computer screen reading. Keep in mind of the text size. Many of the nice flash sites use really small text, but it is difficult to read. If the user is trying to get information, they won’t appreciate it if they have to squint really hard or lean in close to the screen. Or try a pixel based font in Flash, those are still quite small, but slightly easier to read.
Just off the top of my head for now, will let you know if I think of anything else!