Arrowheads and the other interesting artifacts you might find are most often made of stone, ceramic (pottery) or bone. Most arrowheads are chipped from stone, usually flint or chert. Many arrowheads, dart and spear points can be typed and dated. Point types will vary somewhat from region to region.
Long before you see an arrowhead, you will probably see hundreds of chips or flakes of the stone that was used by the Indians of your area. These flakes are the best indicator that you are on the right track, and sometimes the flakes themselves were used as blades or tools. If you are curious about ancient stone tools, it might be interesting to examine all large flakes to see if they were specially shaped into drills or scraping tools.
Learn to examine broken or flaked stone to determine if an Indian worked on the piece seriously or if the piece is simply a burned and cracked rock. With a little practice it is easy to see where flakes were intentionally removed.
A stone that has a cleanly removed flake that shows ripple marks on the flake scar was almost certainly chipped by man and if it is found away from where heavy equipment has operated it was likely done by an Indian. A stone that has multiple flake scars is almost certainly an ancient artifact.
It is not a good idea to try to keep every piece of worked rock you find. These scraps can help show where villages lie and have no real value. After hunting for awhile you will see how common worked stone really is.
While looking for arrow points you will frequently come across other things of interest.
In addition to arrowheads, Indians made fine pipes, jewelry of hard and colorful stones, and fine ceramic ware with incised designs.
Historic sites often yield coins, jewelry, musket balls and fine brass buttons that are very easy to date.