The basic premise is this: on Christmas Eve, you lay out the pickle ornament in front of the tree with the milk and cookies for Santa. Then, Santa hides the pickle ornament. In the morning, the first person to find the pickle ornament receives an extra present from Santa--in our family the extra gift is usually some sort of candy.
For the last several years, Target has carried pickle ornaments for $2 or $3, which also makes it an awesome White Elephant gift. We plan to take the pickle as our White Elephant gift to Justin's work party this next Saturday along with this "pickle poem" explaining the tradition:
To start a tradition that will surely last,
here's the story about the pickle of glass.
The night before Christmas it's hung on the tree
Santa does it secretly.
And on Christmas morning when you arise,
the first to find it gets a sweet surprise.
A family tradition for all to share,
you'll look for the pickle year after year