Okay, we have setup SpringSource Tool Suite (STS) for Groovy and Grails support, but how do we create new domain classes or controllers? Once we have created a Grails project we can press Ctrl+G (in Windows) in our editor and a little popup shows where we can type Grails commands. We get code completion for the commands we can type so it easy to execute them.
The output of the commands is shown in the Output window.
On the Grails website there is now also an article on Groovy and Grails STS Integration.