Keep the number of terms in your glossary quite small: In our practical experience, 10-30 terms were often sufficient to explain the really important things.

You don’t want to write another encyclopedia or re-create wikipedia in your glossary!

Avoid trivia, include specific terms from the problem- and solution space of your system.

Neither “UML” (abbreviation for “Unified Modeling Language”) nor “Java” (programming language) need to be explained in a glossary.