The first time the person hunts for the glasses, the symbol gets loaded. The next time, the eye glasses are shown laying somewhere, we know what happened. Another example, if a gun is always left in a particular spot in a gun case, and then it isn't there, we know something is up with the gun. These symbols alert the viewer that something is going to happen. Another use of symbols has already been discussed.
People surround themselves with symbols of their identity.
If someone carries a briefcase, this conveys information that this person is involved in a business or profession. The person who wears a baseball cap, or has them displayed in his rear car window, we know likes baseball. Symbols tell us about people without having to go into their entire history. For example, a man who wears a Rolex, has a living room full of Chinese furniture and art, has a statue of Buddha in his bed room, a New York Yankees cap hanging on one post of his four-poster bed, and has cowboy boots in his closet, has told us a great many things by symbols. Money is important to him.