I'm almost 46 years old, and I began hunting artifacts when I was 6, so I think that I can give some sage advise to the budding amateur archaeologist out there.  I just read someone else's guide, and it really only made one point...if the price is too good to be true, then it probably is.  No kidding.  The man does have a point, but I don't think his brief essay gets that point across...you need to educate yourself.  Look first at the authentic points you have found yourself, or those found by your friends or relatives.   These will give you a good starting point as to what "looks" right. 

Next, you need to borrow or invest in some quality reading material by knowledgeable people.  Here in my home state of Ohio, the first book I would suggest would be "Ohio Flint Types", by Bob Converse.  I would call this the BIBLE of Indian flint tools in this and surrounding states.  In this booklet, you will be informed as to what types of flaking (percussion or pressure retouch) you should observe on a particular type of point, or if and where you should find grinding present.   You also will learn what types of flint were commonly used to manufacture certain types of  points.                         

If you plan on purchasing artifacts (sales, auctions, eBay, etc.), I highly recommend a pair of books written by James R. Bennett.  "Identifying Altered Ancient Flint Artifacts I and II " will explain what equipment is best suited to examining artifacts for authenticity, what to look for, and what to avoid.  They are well written and illustrated, and are worth their weight in gold!                

Also, I would invest in a good book on flint knapping, and maybe even try my hand at it.  Again, you will gain useful knowledge as to how a certain point should look as far as flaking and grinding, and you also will become more familiar with patina, the mineralisation that forms on the outer layer of the artifact's surface. D.C. Waldorf's "The Art of Flint Knapping" is my favorite book on the topic.  One word of warning...  I beat the H*#! out of my thumbnail while learning to knap!  So will you...

Listen, this is an awesome hobby as long as some skunk doesn't ruin it for you.  Reputable modern knappers identify themselves as such, and the quality displayed by some of them still demands a considerable market value from their work.  But most of us want original pieces, and there are many unscrupulous knappers out there looking to take advantage of the uninformed or unwary by passing off their work as authentic, ancient tools constructed by the original inhabitants of the new world.

Take my advise...do your homework!  If you do, that fluted point with no grinding on the base and the bottom third of the point will look fishy, as will the vast number of "Flint Ridge" paleos.  Likewise the large and beautiful Adena knives that seem too perfect (the Adena and other woodland peoples used very little or no pressure retouch on their flaked tools, as a general rule of thumb).  Did I mention heat-treated chert, or the "fractured base" technique?  These are things you should expect from some point types, but never in others.  A large E-Notch Bevel made of black obsidian would be preposterous, but in a later Hopewell point that material would be expected.

Finally, you can apply my advice to stone tools, too.  And an added benefit will be that you'll start to find stone tools that are barely visible, because you start to recognise pecking and grinding used to shape them.

Hope I've been of some help, and good hunting!