How can you tell if nic nacs are worth anything

Google it. Or get a book on the item you have a question about, they have several in the store.

Know what your looking for, and I agree you need to do your research.

A keen eye and years of experience in collectables. Research research and more research.

If you are looking for some advice, you can call the Mall, tell them what you're looking to sell, and they may be able to match you up with a dealer who knows that stuff.

Best way is to google it.