To be quite honest with you, I'd look for an instructor. A good one will not only get you casting, but should walk you through equipment, entimology (sp?) and working/recognizing streamside.
If this is not possible, get a couple of books. I had exactly one (1) class for casting and such, but I read the heck out of anything and everything that I could. I recommend at least the following books:
Fly Fishing Basics (David Hughes and Richard Bunse)
This is a very basic book, but it's concise and informative. It won't fill your head with alot of stuff that, although you'll need to know, will only serve to confuse you in the beginning.
The L.L. Bean Ultimate Book of Fly Fishing by Lord/Telluer/Whitlock
There's alot of good stuff in this, expands a little more than the first book.
Lastly, pay attention to what is said here. I learned alot from reading stuff here and just getting on the water. It's a real bummer learning stuff with no guiding light, especially at streamside. But, like anything else, it comes with practice and doing it. There is no other alternative.