Adobe actually has a book, photoshop classroom that gives step by step instructions on how to do every thing in photoshop. There is also a CD to go along with the book that has actual photos you can use and follow along and do it yourself.
Hands on is the best way to learn. You can also find many websites that give great photoshop tips, which is how I learned. One that I get tons of great helps from is www.shootsmarter.com.
Once you find a tip, my advice is practice, practice, practice what you have learned. Don’t give up. Photoshop uses layers, be sure you save frequently when you are learning to do something. This way if you make a mistake and it was several steps away and you can just go back to the last save. Then you don’t have to start over and create any more frustration for yourself. Once you learn it, you will love it. I do!