This an intermediate tutorial. I am just going over some extra tips to get a very nice crisp cut. It isn't very indepth, but it should help you.
The first step as always is too find a good high-resolution pic. Check the Photoshop Resource thread for some places to get those. Here's where my way starts. Let's say your image is 800x600, re-size the image to 1600x1200 (this will make sense shortly). At this point you should use the pen tool to make a selection around the pic (see the bottom of the post), I zoom in to about 400% to do this. Get everything right there, and then right click-->make selection-->feather 1 pixel. After this invert your selection and delete the rest of your image (or copy it to a new image if you cut directly on a jpeg). Now does the feathering make sense? If not here it goes. When you feather at the original resolution it is far too obvious and you can't get a crisp line. By upping the resolution you do the equivalent of feather at 0.5 pixels, which keeps a crisp line, but helps smooth it out.
For the actual pen tool work, look at End Bosses tutorial. It may seem intimidatingly difficult. But it's not too bad. And VERY good.
Professional Masking Tutorial.
Masking/Cutting Hairy Players.
Hope all of this helps.