Google Image Result for http://www.agilemodeling.com/images/style/useCaseOnlineShopping.gif
This is the best UML book I have ever seen
Get more data here at UML 2 Use Case Diagramming Guidelines
UML 2 Use Case Diagramming Guidelines
Most people I have worked with don't generally use UML and that is a shame. Perhaps the simple drawing seems childish, perhaps the simple elegance of this mathematics of clear thinking confuses people. Yes requirements gathering, analysis and design can be this simple.
Look at the document up top. To many people this would simply seem like pointless truisms about a profess. And that is precisely what they are, and once you and the stakeholders have agreed the process can be quickly fixed in to a contract of business requirements. Requirements which can rapidly be converted to technical solutions.