Play with language. Rhyme, use figures of speech, symbols, and riddles. Think of crossword clues. Also, be sure to match the difficulty level to your intended treasure hunters!
You might be more inclined to use more riddles and less questions for a treasure hunt since that makes it more simple and it's still challenging without having to depend on some obscure data that the participants may or may not know.
Some good questions for a treasure hunt would be to find something old that might be worth money. Some type of antique that may be a diamond in the rough. Sometimes what you think is trash might be worth money, like old bottles and containers that you find out in the woods.
