There's a few parts to this: Shooting the video clip, getting it into your computer, and then sending it to your friends.
Shooting a video clip: If you already have a video camera, you can shoot a clip of a move and review it until you get a take that you're happy with. That's pretty easy, it just takes time.
The part that's confusing is getting the video into your computer. If you have a recent video camera, it may have a Firewire connector on it (usually the new Sony cameras have this.) If you also have a recent computer, and it has a Firewire connector, then it's a very easy process to hook the camera up to the computer and copy the video to the hard drive.
But from your question, I'm guessing that you haven't spent the money on a new camera and computer recently. If you've got an older camera (or computer), then you'll need to get one of the various video capture gizmos, that allows you to digitize the video from your camera onto the hard drive. Some of these are cards that install into your machine; others are external devices that can plug into the USB port.
I did a quick search on CNet for "video capture" and found that the lowest prices for these devices is about $70.00.
The other option is to get a web camera. This is a small camera that attaches directly to your computer, usually through the USB port. The advantage that one of these has is that you just do the move for the camera, and it's recorded to your hard drive with the software that comes with the camera. It's easy to use. These are now available for under $50.00.
The disadvantage is that the quality you get from a webcam is lower than if you taped a clip with a regular camera and then transferred it to your hard drive. But if you're just messing around, and want an inexpensive solution, a webcam can work.
Once it's on your hard drive, you can send it as an attachment to an email. Be careful not to send huge attachments to your friends, these can take a long time to send on both ends.