copied from the geocache website
FOR THOSE INTERESTED IN GETTING STARTED. MORE TO FOLLOW
Cache Containers
Start by choosing a container that will withstand the weather all year round. Geocachers have had good success with clear, watertight plastic containers, ammunition boxes, and waterproof boxes often used on boats. You will also want to invest in zippered plastic bags to further protect the cache contents, in case your container does leak. View sample Groundspeak
Cache Containers.
Whatever the container, make sure to clearly identify your cache as a geocache. Most geocachers mark the cache container with the words "Official Geocache," the name of the cache, and appropriate contact information. The more information you can provide, the better.
Cache Contents 
Next, you will need a logbook. Make sure to place a writing utensil in the cache as well. If you are in an area where the temperature drops below freezing, make sure to provide a soft lead pencil. Pens tend to freeze and are rendered useless.
Include a
note to welcome the cache finder. The note has been translated into several languages and explains the activity in case someone accidentally finds your cache.
Lastly, you can put items for trading into the cache. It is highly recommended, but not necessary. What you place into your cache is up to you, budget permitting. Some ideas of items to give as goodies:
- Disposable camera. Put one in and ask everyone to take a picture and put it back in the cache. Later you can develop the photos and place them online.
- Toys for children. Include action figures, games, playing cards, and more.
- Trackable items.
- Keys to a brand new car

People of all ages hide and seek caches, so think carefully before placing an item into a cache. Explosives, ammunition, knives, drugs and alcohol should not be placed in a cache. Respect the local laws.
Food items are always a bad idea. Animals have better noses than humans, and in some cases caches have been chewed through and destroyed because of food items in a cache. Please do not put food in a cache.