Collect one big and 10 smaller stones. Every stone has different characteristics. Optimal would be flint, chert, obsidian or other conchoidal fracturing stones, but you might not find those on campus. Anyhow let us see what we can encounter: Try to find stones that look like fragments from bigger parts and search for stones that splinter if you hit them with another stone. The big stone should perfectly match your hand. This stone will be your hammer tool (see flintknapping on Wikipedia). It should have different kind of sharp edges and corners, and it should be hard. You will use it to hit the smaller stone pieces and transform those into arrow heads (like the ones that you can buy from Amazon). Bring your stones to the next meeting and take them to our weekend trip!