It is difficult to tell the difference between an ancient point and a new one if the maker of the point is trying to fool someone. Some trust in a patina of age being a true test, but it can be faked so falls into the category of being an indicator. Also some places where old points are found just don't put much of a patina on stones and some do. Wear use analysis is sometimes helpful unless a modern person goes to the trouble of sawing on a deer with their point. You can also look at the edge microscopically and look for evidence of copper or other modern residue. The best evidence to know you have a genuine point (if it's valuable) is to have found it yourself or very much trust the person who says they found it. Also rock material can play a factor. For instance you would almost never find an obsidian point in Florida. Also if you really know your various points, you can look for things like flaking pattern, basal grinding, size, shape etc that are all indicators. There is alos motive of the owner - Why do they have it? What are they doing with it? Is it merely an asset or is it a prized possession they want to keep?
Generally, I can tell an authentic point by the above methods when I see one, but if someone is trying to fool me, they could probably do it. For this reason, if it really matters, I wouldn't trust someone with a motive to have a fake or a point where money is on the line unless I can establish where it came from and who found it and go from there.
All that said, newly knapped points just look new because there is no dirt on them, the edges are perfect and the shape is almost always likely to be "perfect." That is unless someone goes to the trouble to decieve.
There are people who "authenticate" points for a living and they, for a fee, will give you a piece of paper saying your point is authentic - they supposedly do tests and examinations. Once you have that paper, lots of collectors swear by it.
Sorry for the long-winded reply - I could go on. I have a lot of sympathy for collectors but I don't want people digging up archeological sites everywhere for profit. I have no problems at all with people sifting through creeks and going over plowed fields.
