You want users to be able to write sentences that are as close as possible to the way they might think about what they want to do. The following plan will help you develop a clean vocabulary that allows users to easily work with your application. The first set of steps will help you home in on the terms you'll use in your vocabulary. Write down sentences. The very first thing to do is to write down as many sentences as possible describing actions that can be accomplished with your application.
Users think differently about the way they accomplish things with applications than programmers do.
Invite users of your application to write down some general sentences. Encourage them to think about how they want to accomplish what they do. Ask them to write the sentences as if they were directing the computer by speaking to it. Include users who are experienced with earlier versions of your application. These users don't need AppleScript experience.