Clipping masks scared the hell out of me when I first started learning Illustrator. It took me some time to work them out, but when I finally did a whole new world opened up for me. If you are new to Adobe Illustrator and are yet to discover this fantastic tool, then read on. I am assuming you have already mastered the pen tool – if not try this really good tutorial from a guy who sounds more than a little like Chris from Family Guy.
(FYI I am using CS5 and a PC.)
In order to show you how incredibly useful clipping masks are I am going to create a simple mushroom house.
Step 1. Create a nice green hill using the pen tool. (I like to have my artboard on, it just makes life easier.)

Step 2. Using the rectangle tool, create the stalk of the mushroom.

Step 3. If you hold down the rectangle tool button you can choose another shape. Select the ellipse and create a nice red circle. (Hold the “shift” key down at the same time and you will get a perfect circle.)

Step 4. Go back and select the rectangle tool and create a rectangle over the red circle (it doesn’t matter what colour).

Step 5. Select both the circle and the rectangle and go to “pathfinder”. Select the “minus front” option. This will remove the shape of the rectangle from the circle, creating the top of the mushroom.

Step 6. Place the mushroom top on the stalk, while it is still selected go to > Edit > Copy, then > Edit > Paste in Front. This pastes another mushroom top directly in front of the original mushroom top. Select both mushroom tops and go to Object > Clipping Mask > Make. If you look in your Layers panel you will see that the mushroom top is now in a group. Expand the group and you will see two layers, the top one is now the clipping mask.

Basically, anything you place between (this is important) those two layers will be inside the clipping mask (which is the exact shape of the mushroom top). So now the fun begins.
Step 7. Create a lot of white circles, varying in size and place them randomly on top of the mushroom top. Select the magic wand tool and click on one of the circles, this will select them all (because they are all the same fill colour).

Step 8. Go to Edit > Cut, then select the direct selection tool and click on the mushroom top.

Step 9. Go to > Edit > Paste in Front, then select the magic wand tool again and change the opacity of the white spots to about 90%.

Step 10. Create a nice orange Sun in the top right-hand corner. This will help you figure out your highlights and shadows. Over the top of the mushroom create a shape – this is going to be a highlight. Use the eyedropper tool to select the same colour as the mushroom top, then open the colour picker and choose a slightly lighter shade.

Step 11. Now cut the highlight and paste it directly in front of the mushroom top (using the same method as in step 8). Still using the direct selection tool click on the highlight and go to Effect > Blur > Gaussian Blur and blur it about 50%.

Step 12. Using the exact same method, create a shadow for the other side of the mushroom top, just select a slightly darker colour. Your mushroom should look something like this…

Step 13. Using the ellipse and rectangle tools create a cute little window.

Step 14. Add a nice blue sky using the rectangle tool, select it and go to Object > Arrange > Send to Back.
Step 15. Go nuts! Now that you know how to do clipping masks you can go crazy with them!

If you finish this tutorial I would love to see what you create, so please hook me up with a link. Also, feedback is very welcome.
Ack, this makes my brain hurt LOL So cute though, I’d love to see some of the link ups from your readers!