Traditional Treasure Hunt
Traditional treasure hunts center on searching for well-prepared clues. The clues direct the players from one location to the next before finally leading to the treasure. Decide where the hunt will take place and look for strategic objects or locations to base the clues on. Write simple rhyming clues as riddles for the children to solve to make it more difficult. Alternatively, write them in code -- this works well for older children or teens. You need to hide a treasure chest or whatever you use to hold the treasure, and make the prizes it contains age- and theme-appropriate. Teens may prefer movie tickets or store vouchers as opposed to candies.
Scavenger Hunt
Scavenger hunts are easy to adapt for any environment or age group. Make a list of objects for each child or teen to find and award prizes based on the number of items they collect from the list. Prepare the list in advance according to the party setting -- it may be indoors or outdoors, or somewhere away from home such as the beach or the woods. A-Z lists work well for older children and teens. Make a shorter list for younger children and include more general items such as "something blue."
Hidden Object Treasure Hunt
Younger children may find it easier to hunt for hidden objects. Adapt the hunt to the theme of the party. For example; at a teddy bear picnic, hide teddy faces cut from construction paper, and see how many they can find. Swap the teddy faces for prizes. For a jungle party, hide plush animals and send them on safari to see how many they can spot. Hide magic wands at a fairy party -- have the children wave the wands and say some magic words to make the treasure "magically" appear.
Around Town Hunt
This game is for teens who have the freedom to explore further afield. Divide the teens into groups of three or four. Provide each group with a digital camera or smartphone to record their discoveries. Give them a list of things to find around town -- it can be an alphabetical list of locations or objects, or a list of questions they can only answer by visiting specific locations. Have everyone meet at the end to compare results over a barbecue or pizza and award a prize to the most successful team.