In school they made us buy Elaine Weinmann and
Peter Lourekas's Visual Quickstart Guide to
Photoshop.  It's around $20, which really isn't
bad (*remembers the prices on Director and
Premiere books with a shudder*), and works like a
tutorial book, taking you through step by step. 
Now, personally...I don't think I ever really
opened the thing *chuckles*.  My mind works oddly
and I didn't much care for the way the Quick Start
Guides were ordered.  But everyone else seemed to
really like them, so it might be worth checking
out at your local bookstore.

For advice, I impart the knowledge that my
instructor, the illustrious Bob (^_~), gave to me:
If something isn't working in image editing and
you're ready to tear your hair out, chances are
it's either the wrong layer or you've got a
selection somewhere.  Honestly, I still remind
myself of this when some effect isn't happening on
the screen even though I'm pushing the mouse
button harder and harder ;).

Talia