Know what you are buying and how much you should pay. Buy reference books, or borrow them from your local library.
Clubs abound in almost every area of collecting.
There are collectors magazines galore, TV shows and of course the Internet. Talk to other collectors. It's the best way to check out the local market. Buy the best you can afford It doesn't matter if you collect diamonds or dolls. Your collection will appreciate faster and if you ever decide to sell, you'll realize a much better return on your investment Check condition.