Think carefully about who and what you will teach. Understand who your students are in terms of their level of English, their level of content knowledge and their requirements. Carefully consider what you will teach, in terms of both content and language, and what materials to use. In some cases you might be able to adapt material designed for native English speakers.
Consider the cognitive load of the material on your learners. You do not want to overload their brains with too much information. Instead, choose relatively simple content or use an area that you have already covered in their native language. In this way the lesson will act as both revision and extension.
Find materials that appeal to your learners. There are many sources of materials available on the Internet. The Center for Advanced Research on Language Acquisition (CARLA) at the University of Minnesota provides texts at the appropriate language level that can be legally adapted and used in class.
Exploit your materials for grammar and vocabulary. Think about the words: you will need to teach technical or specialist vocabulary that your students need to know for the course or to understand the text. Also look at the grammar structures that commonly appear. You will need to concentrate on general comprehension.
Develop follow-up activities that reinforce vocabulary and develop language skills and comprehension of the topic. These activities can include group discussions, individual presentations, preparing posters and writing about the topic.