You will probably be asked to prepare a syllabus for your course and in your first class you will probably want to tell the students what you are going to accomplish. That's important to do and in this way the administration and the students will know what to expect.

No less important, however, is to define specifically what the course will not cover. Students and administration may expect you to cover everything that is assumed by the title of the course and at the end of the course they may ask why you didn't cover a certain feature or aspect of it. Your goal therefore, should be to limit their expectations, to say what you will teach, yes, but also say what you will not teach.

For example, if you are teaching a course about writing reports then you should define in the beginning whether it also includes teaching grammar and how to write sentences or whether that will be left for and expected to be taught by a different teacher. If you are teaching web design, then you will tell them whether they are going to learn Java script or whether they are just going to learn how to create a web page or a website using Notepad or a basic web development program.