Call out the person's name, tap the person on the shoulder, or wave. Key the person into the topic. They need to know what the subject is to be able to pick up words that will help them follow the conversation. Speak slowly and clearly, but do not yell, exaggerate, or over pronounce. Exaggeration can distort lip movements.
Short sentences are easier to understand.
Look directly at the person when speaking. Avoid turning away. Do not place anything in your mouth when speaking. Maintain eye contact with the person. If an interpreter is present, continue to speak directly to the person with the hearing impairment.