This tutorial was made for Photoshop 7 on a PC.  The effect we're going for here is one you might have seen on an iPod commercial, with the black silhouette of a person on a white background.

 

There are two ways to cut the boy out of his background.  One is the Polygonal Lasso Tool, but I prefer the Pen Tool because it allows you to correct mistakes you may make.  This tutorial uses the pen tool.

Select the pen tool (REFERENCE) and make sure that Paths is selected up top (REFERENCE).  Basically, you have to manually cut along the outline of the boy by clicking all along the way.  You will catch more detail if you click more often, so to be very accurate, zoom in using the Zoom tool.

Now, what I SHOULD have done is selected all along the boy's outline, but for some reason I went about selecting the background instead.  No problem; it will give me the same results, but this means I need to do it in chunks instead of one continuous loop.  When the boy's outline hits the edge of the picture, click back around outside the canvas and wrap back to the starting point (REFERENCE).  Then start on the next section.

If you mess up, use the Direct Selection Tool (REFERENCE) to select one of your points and move it.  When you are done, you should have everything outside of the boy's outline selected.

Now, create a new layer named Silhouette, and make sure your foreground color is white (REFERENCE).  Still using the pen tool., right click and select Fill Path... . Make sure it is using Foreground Color and select OK (REFERENCE).

Your layers palette should look like this.  Create a new layer between the picture and the silhouette layer, named Black.  Switch your foreground color to black, select the Paint Bucket Tool (REFERENCE), and fill this layer with black.  Selecting the pen tool again, right click and hit Delete Path.

Here's what your layers palette should look like:

and here is your final product!

When you get really good with the pen tool, you can even start curving your lines for more accuracy, but I'll leave that for another tutorial!