Well, not sure what all I can say today. I have a couple of suggestions though that I think will be a great help to some.
First, Curves Curves Curves!!
Figure this function out ... I am still learning but go in and do some playing. There are alot of different things that you can do in Curves and you can really enhance a photo or you can really destroy a photo. So when you decided to start playing make sure you are not working on your original photo so that if you do mess something up you don't destroy your original.
I was introduce to the concept of Curves in a Seminar that was instructed by Ben Willmore. This man has a great understanding of Curves and I bet would be awesome to have a one on one class to learn from him directly.
Do some research on Curves, Ben has written a Photoshop Book, couple actually where he does talk about and go through some Curves.
Couple of Sites that might Help You:
Sample from Ben's Book: http://www.peachpit.com/articles/article.aspx?p=767329
Ben Willmores Utube Videos:
Digital Mastery ~ Ben Willmore: