If you're just looking to do that use the laso or the magic wand. Yes, it takes a lot, and I do mean a LOT of practice just to get good at it, let alone really good. And to master it? Forget it. I have a degree in Graphic Design and other than the instructions above, I wouldn't know where to tell you to begin. Hmmm. Tutorials in books. Adobe's Classroom in a Book is a good place to start. Take a class. Photoshop, especially when combined with other Adobe products is simply a phenomenal tool. Don't give up, just be patient.