Good point about 'asked'. Since posting this thread that has stuck out to me all the more when I've written it. I think I would always go for 'asked Dave' instead of 'Dave asked' unless the tag came before the speech. It just seems to make sense to have 'asked' next to the question being asked. So similarly with 'said', although variety must be considered and perhaps with rhythm being the clincher.
Andy
I think it was Stephen King who advised that 'said' is invisible word in dialogue - and he has sold a few books.
Cheers
Michael