Basic usage, and things to be aware of that can help you in your day to day usage of GWT-Maven.
The fastest way to get started is to use the archetype, see the one-liner there.
Run the GWTShell - mvn clean gwt-maven:gwt
Build a WAR - mvn clean gwt-maven install
This plugins prefix is now "gwt-maven" (it used to be just "gwt", but we ran into a conflict with the Codehaus GWT plugin - long story).
Like any good Maven 2 Plugin, the generated plugin docs contain documentation on all the goals and configuration parameters. See the goals docs (also available from the left hand menu).
If you want to skip the GWT compilation step for any reason (which, for example, makes the shell launch a lot faster after you know you have already compiled), you can using the google.webtoolkit.compileSkip system property.
Also see the testing docs for a lot more testing information.