To learn the value of your dishware, you first need to identify what you have. Check the bottom of the plates to look for a back stamp. Marks on the bottoms of plates, bowls, cups, etc. can help you learn who manufactured the pieces. As companies often made slight changes to their marks, these differences can help you date the dishware. There are many informative books on the subject. It's best to narrow down your search. If you look at older price guides, remember that values change over time. So the stated value in an older book will not reflect current prices.
Once you get an idea of who made your dishware, you can find values online at Kovels, Replacements, or Worthpoint. You need to establish an account for specific values.