Teaching writing skills can be quite challenging as each student has different needs. Some students are planning on taking advanced tests like the TOEFL, whereas others just want to use English during their travels abroad. In general, it's important to focus on encouraging writing skills that students feel they will actually use. It's a good idea to start off with short writing exercises, and then, if it makes sense for the class, move on to more advanced skills such as writing essays. Use a writing rubric to grade longer written assignments, as this will give students a broader overview of the skills they need to improve.