Littlejohn,
Good point. I've thrown down many times a piece of flint only to pick it up again and see that it was a bird point or scraper. Especially my first year out. While it may be controversial, I tend to latch onto anything of interest. You can always return to rocks to the area when you've determined that they are of no interest (I've actually done this). For interest, I've attached a photo of what would at first glance to be trash. If you'll look closer, notice the several pieces of pottery, broken points, and scrapers. Also, numerous flint flakes. The important thing is to continue looking. Then, research what you've found. There are numerous places (such as this) where identification can be made.
Good luck!
docmann