http://www.good-tutorials.com/ has a lot of tutorials, and not just for Photoshop.
As a beginner I think the best thing for you is to simply know what looks good and what doesn't, and how to produce the same effects that you see in signatures you like.
The quickest way to go about doing that is to read as many tutorials as possible, especially tutorials that are out of your league (but no so much that they don't tell you how to do something).
If there's a specific effect or quality that you saw in a sig that you'd like to learn how to do, post in this thread:
http://forums.d2jsp.org/index.php?showtopic=18159470&f=105If you have a specific question about where things are in Photoshop, either post in this section or PM another member

Most people are glad to help.
NintendoGun's Tut/Resource Compilation:
http://forums.d2jsp.org/index.php?showtopic=10325235&f=246