Simplify your vocabulary, grammar, and speaking speed to the degree necessary to be understood, and keep any instructions simple and logical. New ESL teachers frequently slow down the pace of their speech but forget to modify their vocabulary and grammar for beginning students. As your students' English ability increases, so should the complexity and speed of your English. Some of your interaction at an intermediate level and most of it at an advanced level can use natural grammar and speed, but make sure you slow down or repeat any highly important points. Teach your learners how to ask for clarification when they need it. Try to anticipate unknown vocabulary and be prepared to explain it. Appropriate language modification gets easier with experience.