Know who attends your library. Though it sounds simple, knowing what your patrons expect from your library will greatly aid you in your cause to categorize the often abstract realia. For example, if you live in an area with historical significance in something like the Civil War, you will want to display objects that may tie the history of this event in with some local families of the area. Perhaps you possess a wallet or a drawing or work of art from an ancestor. With this you can set up separate displays categorized by each different family. Think creatively and draw on experiences with your community.
Develop a comprehensive online database of your library's realia. Just as the Dewey decimal system was dropped in favor of an online database for books, realia must also be categorized online so that your patrons can easily find what they are looking for. Though it will take some time and more than likely a grant or loan from the community, this is still an essential upgrade to how your library categorizes its realia. Using an online database, you can break down how you show your realia by categories such as age, type (for example, statue or art), and historical significance.
Display only a portion of your collection. Most libraries contain more realia than they will ever show at any one time. Choosing which realia to show will make the process of categorizing all of it easier. Plan out cycles for showing various works. In February you can put out items relating to black history for Black History Month while in the summer you can cycle through items related to Independence Day and the founding of America.
Divide up the realia by historical significance. It sounds simple, but some items carry with them greater historical significance than others. You will want to separate these items and place them in strategic parts of the library. Place more important pieces at the front of the library so that your patrons can quickly view them, for example. Perhaps you may place these more interesting pieces next to information on your library and any budget concerns or programs you are launching. The other more niche-history items can then be placed throughout the library in sections that relate well to them. Items such a baseball glove or bat can be placed next to a sports section, for example. This will make your process of categorization much easier. Remember to stay creative and use the realia to add different levels to the texts your library possesses.