Basically, a big circle for the head and two smaller circles for the ears. There are also some Hidden Mickeys that look like Mickey's profile, more like this (I have yet to find any personally that look like this one):
I won't begin to go into where you can find them within the Parks. There are thousands of them, all over everywhere. There are entire websites and books dedicated to this subject, and I highly recommend checking them out if you are at all interested in finding them. The Parks sell one of the books or you can order one easily from Amazon.com. If you have the MouseWait app on your phone that I mentioned in a previous post, they have a special section called Hidden Mickey Checklist where you can check off and keep track of the ones you have found.
Below you will find a few of the Mickeys that I have found myself...can you tell where in the Parks they are?? Some are a lot easier to spot than others. Good luck and happy hunting!!