I'm always amazed at the information some of my other vintage-seller-friends have stored in their brains! They've come to my rescue more than once with great info!
I have a pretty good eye when it comes to knowing if something is actually over 20 years old or not. I buy the things that I love, so if they don't sell, that's okay...I can keep them!
I bring home my loot, and then start researching. The internet is a good place to start, it's amazing how much good information you can get these days!
I am constantly borrowing books from the library too! That way, if I find ones I really like, I go on over to Amazon.com to buy them (you can get used books that in in excellent condition, at a great price).
I've acquired quite a collection of research books. The ones I'm showing now are some of my all time favorites!
Some of my favorite milk glass pieces are Westmoreland and Fenton.
For my china shop I love this reference book for markings:
My latest book purchase was The Hazel Atlas Glass Identification & Value Guide, by Cathy & Gene Florence. I have some many pages marked, as I have several pieces that are listed in this book!
I learn new things everyday about vintage and antiques! It's fun!