For starters, I suggest that you print this page and take it with you when you are making an outing to a flea market, art gallery, dealership, or art show. If you are embarrassed to bring it with you, just leave it in your car and consult it before you begin your shopping. Personally, I've gotten over the embarrassment thing because art purchases are important and questions are warranted. You don't mind the age and you shouldn't mind it, in most cases. You even find that the old frame is growing on you.
People love bargains or love to believe they are getting bargains.
You have to have an idea of what you are buying. Yes, I meant to scare you. I did it on purpose. I apologize but this is how you can be really taken for a ride. I'm going to educate you so you can make smart art investments and purchase good works of art for your collection and enjoyment.