the best pointer i can give is to watch tutorials, its basically the only way to learn all the tools that photoshop has to offer...things like blending, using multiple stocks in the background, player effects, and gradients are really important in making sigs and these are all things u can learn from the tutorials on this site and on http://www.psdcentral.net
for your first sig, you got the play placement/sizing down very well. i like that. text is alright as well, but the bg is no good, actually distracting. you have to blend some other pics in the bg so its not just a pattern. but this is a good start. keep working.