Math Problems
Reinforce what you've recently taught students by providing clues that contain math problems that need to be solved. A clue could say something like, "The answer to this problem is the number of the room that holds the next clue. Hint: Look down!" Another idea is to focus on geometry. Give students a list of shapes and have them prowl the school grounds for common objects that fit those shapes. Have them record the object next to the name of the shape.
English Trivia
To add an element of English, include a clue that leads students to a book or poster of a famous author. For example, if your school library has a poster of Robert Frost, your clue might say, "I stopped by the woods on a snowy evening once; maybe that's why I sound a bit cold. I'm trying to warm up in the library." You can also use this clue to point to students to Robert Frost books, and plant the next clue in one of his books, or on the shelf the books are on.
Science
Look around the school for any scientific props where you could place clues. A skeleton is one example. You could use a common riddle such as, "I didn't dance, because I had nobody to dance with. Who am I?" Italicize "body" in the word "nobody."
Art
Lead students to a print of a famous painting, or to a spot in the art room where the next clue awaits them. "I'm repainted every day, and every day the paint is washed away" could lead students to the cupboard where painting palettes are kept.
Online
Students can also search for clues online, which can help them hone their Internet research skills. Revolve the hunt around a theme. Have students pair up, and assign each pair to a computer. Instead of planting clues, give them a list of things they must find, such as a credible site about the history of jazz, or a recent scholarly article on psychoanalytic theory. Specify what a credible site is.
Library
You could hold an entire scavenger hunt in the library, to help students get used to using the catalog and finding books. Have them work in pairs or small groups so they can help one another. Place clues within books, tucking them in like bookmarks so students can easily see them after they've picked up the right book. As with any scavenger hunt, they should leave clues in place after they find them so others can continue hunting.