I don't do geocaching, but I do something called letterboxing. It is very similar but doesn't require GPS, so if you don't want to wait until Christmas, go now! (Many people do both in fact.)
go to www.atlasquest.com
Bascially, letterboxing requires you to have a rubber stamp, ink pad or ink pens and a notebook or paper of some kind. You find clues and go on a scavenger hunt. When you find the box, you stamp into their logbook (notebook) and sign your trail name and date and a message if you wish. Then, you take their stamp and stamp the image into your logbook with the name of the letterbox. Return their stamp to their box or bag and hide well. Then find another!
You can also find "hitchhikers"-take them with you and then plant them at your next find. See how far it has traveled!
atlasquest divides the clues into categories-how long is the hike? is it indoors? do you have to pay to get in? is it a mental puzzle or self explanatory?
There are also mystery boxes-very vague clues or sometimes just an image. Sometimes a box will lead to another. DH and I found one that was about Gumby. Gumby then led us to Pokey!
It's fun. We just went yesterday when we were up in Portsmouth, NH. Did some short hike ones that were stroller friendly. It's great because you start seeing some familiar names who all must be locals too!
(And then you get into stamp carving, which is a whole 'nother hobby!)
For anyone else, our trail name is TwoBrownDogs and Alex.