The people at MigLayout have setup a great demo that lets you learn how to configure the miglayout through experimentation.
Go to http://www.miglayout.com/ and select Swing Demo. You can then see sample uses of the layout and more importantly, you can right-click on any component (textfield, label, etc.) and change the layout constraints. This is an excellent interactive tool to learn about the layout and how it will work with resizing, etc.
