These key caps are extremely easy to break. So going in prepared is key. :)
If you haven't taken a look at the internals of the key switch here's a picture that will probably help more than anything.
[image|3501839]
This image is a bit newer model, but the mechanism is largely the same. The key to damage free removal is to use something slim (like [product|IF145-259|iFixit's Jimmy|new_window=true] or an [product|IF145-130|iSesamo|new_window=true]) to get under the top edge of the key cap. That's the side with the clips, and the bottom edge has a little hinge in each corner that can take the posts on the key switch out too if you're not gentle.
[guide|139192|There's also a Guide] if you want a more step by step.