RESEARCH CACHE AREA
Buy a map, preferably a topographical map which shows the features of the land, to get an idea of the area. This will prepare you for crossing a creek or climbing rocks, and it will give you an idea of how far you might have to hike to get to the cache.
Geocaching.com uses a link to MapBlast to help show where the caches are hidden, and you can zoom in or out on these maps to see the area. But they can only zoom in so far, so the topographical map is preferred.
If you are familiar with the area, or it is small, you can use only the GPS unit. But this is not recommended for a first try.
STAY AHEAD OF GAME
Always bring someone with you. You probably won't know the area, and it will help you a lot if you have a partner.
Keep your head up and look around the area when you're walking so you don't step in anything or run into anything.
Always bring water, and don't drink directly from a stream.
Always let someone know when you're leaving and when you plan to come back.
TIPS ON SEARCHING
Bring a compass if the GPS unit doesn't have one.
Make sure you mark the location of your car (you can do this in the GPS unit, called a waypoint), so when you get deep into the woods, you can find your way back.
When you get within 300 feet of the cache, remember that the signal is not exact and try to use a compass for at least the last 30 feet. This is the hardest part, especially because people can hide the container just about anywhere.
WHEN YOU FIND CACHE
If you take an item, leave an item, and write in the logbook if there is one.
Make sure you seal it good and put it back exactly where and how you found it.
Use the waypoint to get back to your car, and when you get home, e-mail the person who hid the cache and let him know you found it.