To help ensure comprehension, there's a few things that teachers can use and/or do. Putting up visual aids is always beneficial for students because they can reference it as needed. It also helps when the teacher uses the target language as the vehicle of instruction and provides the students with rich input. Along with the target language, gestures and motions to help reiterate the meaning of certain words helps guide the students. Essentially, teachers should focus on repetition, interaction, and reinforcement to help ensure comprehension. One big no-no is explaining something in the L1 prior to or after saying it in the target language. In doing so, students will learn to expect it and not attempt to comprehend the target language.