I wouldn't know where to start. I only know the barest minimum about Photoshop, and none of it is really applicable to processing images. Or, if it is, I wouldn't know what I'm doing any way, so I'd probably end up with terrible pictures. I've gotten okay at processing images for my online classes, but I basically just fiddle with the controls until it looks ok. 
Well, there are two ways to approach this situation. One is is to learn the program inside and out with encyclopedic depth. The other is to start a project of some sort, and use that as a ground for gaining new knowledge. Photoshop is big, and most people learn better in a more project oriented format.
So what I suggest is starting a project of some sort, then before you touch anything, decide things that you think need to be done. Then get some one else to add their two cents as to what should be done and whether or not you agree with them try and understand the reasoning behind it. Then its project time, start up and try and accomplish just the things you set out to do and see where you end up. By this time you will find you are likely missing some steps that would help alot...Which means you are back to step one. Figure out what else needs to be done, or should have been done previous, then its back to work again
Of course have some reference or people on stand by for the getting to work part so you can learn the tools quickly. The idea really is once you have gone through one time and asked some one who has an idea of what is going on you will hopefully get responses that help you understand tools that you didnt know about, and ways to work with whats available. Just about trying to think with what you have, while you learn what you have.
Henning: Yeah it is. That little guy was about 10mm +/- I also stopped down quick alot.
