While the erase method does work there are easier and more thorough ways to extract on newer versions of Photoshop. (Never use the extract tool or the magic wand if possible.)
The two best are using the lasso tool and the pen tool.
Here is a link which shows 5 different ways of masking including:
* Using Photoshop's Magic Eraser tool
* Using Photoshop's Background Eraser tool
* Using the Extract command
* Using Quick Mask mode to make a selection and layer mask
* Using the Pen Tool to make a selection and layer mask
5 Great Background Masking Techniques in Photoshop
That's a great link Tribal Dancer.
Maybe I am in the minority but I tried the mask tool using the erasers and brushes and hated it. I ran into the same problem I had with just erasing everything, that even after I thought I was finished I would find I had missed a spot or the image would have a halo around it.
It is quick masking with the pen tool however that all my friends love using. No halo and it is very, very, precise. They also use the pen tool to make original art or "vectors" by using the color fill and outline options. I know, I know, someday I have to bit the bullet and give it another try but until then I'll stick with the polygon lasso and 300%+ magnification. It's just easier.
uh... I guess I should give some more links so I'm not just babbling.
Photoshop’s Image Masking Tools
Pen Tool Tutorials
BTW In PS CS4, they added a new tool for quick selection it is pretty good and simple to use for most jobs ... so don't hold dearly into your old version of the software.
Yes, the pen tool works when you have a precise object with sharp edges and good contrast. It can be tricky and harsh for other subjects.
It is THE tool for Illustrator, and is great for very precise lines and shapes!