That is a very good tutorial for a quick fix. If you have a project you need more precision with, here are a few tricks for having more control.
1. Make a copy (or 2) of your original image on a few layers. Turn the bottom layer off so it is your "safety source".
2. Use the lasso as described in this tutorial to isolate your subject. IMPORTANT: grab too much, not too little. Also, don't use a soft gradation on your lasso, it can give an unwanted flimsy effect.
3. Make a spare copy of the cutout and turn it off. Add a blank layer and fill with a solid color to make your cutout subject easy to see.
4. Now use the magnifying tool to get close to your border and use the ERASER tool with as fine a point as you need. If it's hard to tell what's what in the blow-up, you can set your background color layer a bit transparent to see the background.
5. Test how good your cutout is. Make a copy of the original picture layer and darken or lighten it. Look at the cutout subject to see if he lost anything like part of his head or hands. Now is the chance to recouperate these details from the saftey copy and put them back in.
6. Using several copies of your background, try different blur settings or the render-lighting effects to create a dramatic light separation.
The main thing I discovered was that the eraser tool can be a great paintbrush!
