Observe the characteristics of the pieces in detail. Vintage pieces have some qualities that are not found in present day dinnerware. Shape of the plates were different in early times. There were coupe plates and rim plates. The former were all the same diameter while the later had a second circle which was intended to be inside. The colors and designs were also different. Many manufacturers were famous for their own unique patterns. For example Haviland produced soft floral patterns. Do not forget to check its quality. The colors and patterns should be consistent on the set. The glaze should also be smooth and shouldn't be bubbled from any place. They should also be stable so that they do not wobble.
Check the backside of the dinnerware. There will be a marker stamp. It is one of the simplest ways to identify vintage pieces. The stamp may have lost some color over time but it will still be visible. The company name will either be stamped, painted or impresses on the back. Some pieces even have numbers printed with the manufacturers name; this signifies the time when it was made.
Do thorough research before purchasing vintage pieces. Go to the library and check for marker stamps and patterns. The art section in the library has books regarding these topics. Search specific names like Wedgewood, to find books about these famous producers of dinnerware. The internet can also help in your search. There are numerous websites that enable selling of china sets. They have lists of multiple manufacturers, along with the descriptions and pictures of the pieces. There are also detailed instructions about emailing them the pictures of your set for identification help.
After gathering all the information, find out how old the piece actually is. After you know the manufactures name, you can determine the age by research. The patterns, stamp colors and the number on the pieces can help in identifying the age.