First - here's a piece of the original image. I have blown up all the images so you can see the detail. When you are working, you will probably want to zoom in so you are seeing the image at 300 or 400 percent, so you can also see the detail. As you can see, there are lots of tiny hairs, and a yellow background. We will be changing to a blue background, but we want all these little hairs to show.I recommend always copying the original image, pasting into a new image, and closing the original, so you don't accidentally save over the first one. I also save in a format that saves all my layers and blend modes, so I can come back to them later and do any changes I want.On your new image, create a blank layer, and flood fill with white. Then paste the copy of your original as a new layer above the white layer. This way, you can see what you are erasing.
Here, you can see the background is gone. I used the background eraser, which is pretty good about separating all those fine hairs and details you want and just getting rid of the background. This works best for images with a fairly uniform background, about the same lightness and color consistently. As you can see, the ends of the hairs aren't as nice and defined as in the above image, but we'll work with this, as it isn't bad either. By the time we're done, they should look ok.
Here's his shoulder, after the background is erased. As you can see, we still have a bit of the yellow, but if you remove all of the yellow, you also remove the shirt. We'll take care of this later.
At this point, you create another new layer, above the white layer, but below the layer of the subject that we are working on. This is where you add the background or image that you want to work in. In this case, I'm working on a blue background. Notice that with the darker blue background you can see things that you didn't with the white background. Now you go back and clean up a little bit more, like the edges around his ear. Be careful not to remove too much
This shows the shoulder with the blue background. This is erased just about right. Now we need to get rid of that yellow "halo".
You want to start by using the eyedropper to sample the background color. Next, in PSP, I use the change to target brush, set to color. I think in PS you could use the brush with the blend mode settings to color as well, both of these should be set to a fairly low opacity. You don't want to change the whole image, just the halo (colored reflection from the surroundings) at the edge.
Here I've used the same technique on his hair and the edge of his skin. Notice that his hair doesn't look blue, it just doesn't look yellow any more. If you want, at this point, you do the remainder of the things you want to the main subject of the image. For example, blending the edges of his hair in a bit or adding a drop shadow.
At this point, you have the option of leaving the image as it's separate layers, or merging them all. ------At this point, the tutorial is finished, but below is another way that I've used when replacing backgrounds. Enjoy, and feel free to ask questions if you have them!Another hint for when you are working with a particularly difficult image, is to duplicate the subject (your cut out item) layer, and then setting the bottom one to darken blend mode. (The top one has it's visibility off in this shot.) This would probably have solved the problem of the little fringes by the ear you saw above. Now, turn on the visibility of the upper duplicated layer, and using a soft brush gently erase the very edge, so that only the "darker" spots show thru. Don't go very far in, as you want the rest of the layer to show. (You don't want your background to show thru.Conversely, depending on the image and the background, you might have to set the blend mode to "lighten". An example would be where the hair is white. You'd want all those little wisps of white hair to show.