I have to agree with "Dug" on that one.
I own and operate 2 website development companies.
I rarely use intros on client's sites unless they specifically request one.
The one thing i have found from doing alot of coporate sites is that the average user doesn't have alot of time on their hands when viewing your site and an intro just makes them move on to the next in their search page list.
If you are going to do intros I also agree that they should at the least have something to do with the site itself.
However if you still need to provide a client with an intro, remember the "cardinal" rules.
1. ALWAYS if there is sound give them some way to turn it off.
2. ALWAYS,ALWAYS give them a "skip into" within the first 10-15 frames of the intro timeline, that way at least you are not running them away if they want to still go to the site.
I hope this helps.
On a side note flash intros are really not taught, just learn as much flash as you can, seek out tutorials and inspiration from my fav site for this
http://www.kirupa.com.
He has some very cool fun stuff in his tutorials and very easy to walk through and learn.
Good luck and keep Flashing.
Kenny