Q: I found an arrowhead a while back, and I've been wondering this. I know I could ask someone that knows about that stuff, but I wanna learn how to determine an estimated date at least.
A: If it's obsidian you can cut a piece out and measure the hydration. That's how much water the stone has absorbed since it was made. Another means would be to identify the region found and the style of the point. Based on artifacts dated from other sites you'd get a date range. As example the Elko eared is found the the NW of the US and dates between 3400 - 1250 BP. Third is to excavate where you found it, run carbon 14 testing and get a date of occupancy. This is one of the "Don't try this at home" activities as the testing will cost $500 and it's very easy to contaminate the material. Suggestion: Find a book on pricing stone points and see if you can find one like yours. Next try a museum