Ok. Application icons can be found by opening Finder, browsing to Applications, and then finding the icon of the application you want. From here, there are two options (you only need to follow one):
- Single click on the application icon and then press COMMAND-I. At the top of the window that opens up is a small icon representative of the application icon. Single click on this and press COMMAND-C. Next, open up Preview and press COMMAND-N. The icon should open in Preview. From here, you can save it in whatever format you wish.
- Right click on the application icon and select Show Package Contents. Browse to the Resources folder. Inside this folder you will find a slew of items including icons used by the program. Select the icon you want and press COMMAND-C. Open Preview and press COMMAND-N. The icon should open in Preview, just as it did above.
Another place to find system icons is \System\Library\Core Services. Look for Core Types.bundle, right click on it, and select Show Package Contents. Again browse to Resources, and look for icons you are interested in. Use the steps above (COMMAND-C, Preview, etc.) to extract the icons you want.
Let me know if this doesn't make sense, and I'll try and help out more.