This FAQ will as soon as time permits (other things have priority) feature a full WMLScript section. If you want to get the necessary primer and introduction to WMLScript, we recommend the following articles and sites:

For a beginner's guide to WMLScript, see this article from ASP Today.

Openwav's Developer site contains lots of useful links, downloads and documentation not only for WMLScript, e.g. WMLScript Reference, WMLScript 1.2 Reference or WMLScript Developer's Guide.

Doc JavaScript (and don't let that fool you) has a couple of articles.

Chapter 6 in "Professional WAP" from Wrox