If you are unfamiliar with UML, this is a great way to learn. Download MDriven Designer and follow along with these lessons.

Watch the video below for a description of the main concepts of modeling.

Lesson 1 Short introduction to UML – class diagram Lesson 2 Association classes Lesson 3 UML Inheritance Lesson 4 UML – State machines Lesson 5 Constraints Lesson 6 Derived attributes & associations Lesson 7 Composite and Aggregate and what they imply