Finding every cache is a success but, if you have junior cachers in tow, finding one with SWAG makes it all the more exciting.
You are looking for a small plastic container, just big enough to hold a log and some items intended for kids to swap and enjoy. One of my few peeves in geocaching is tat - the items are things children would be pleased to find. Please, do not take them and leave a penny, a single playing card, a bottle top, business card, etc. Leave something that will bring a smile to the next child.
The cache is in a place that children can easily guess and retrieve. Please take care to cover it with the obvious item when you're done.