You also asked about which 30x redirect to use. I'm also looking for this answer. We currently an ASP header redirect. I don't think this is best, but I'm not sure a 301 redirect can be used. I'd like to hear from others too.
This is what we have now:
lang = Request.ServerVariables("HTTP_ACCEPT_LANGUAGE")
real_lang = Left(lang,2)
'Response.Write real_lang
Select case real_lang
case "en"
Response.Redirect "/en"
case "fr"
Response.Redirect "/fr"
case "de"
Response.Redirect "/ge"
case else
Response.Redirect "/en"
End Select