You will want to simplify everything as much as possible. For example, give just one direction or piece of information at a time. Ask just one question at a time. A nticipate problems. Be prepared, for example, to repeat yourself many times without losing your temper.
M ake eye contact before speaking.
Sometimes a gentle touch, if appropriate, can be a way of making sure you have the person's attention before you begin speaking. L isten to how you sound. If so, you may sound angry or upset. Even if the impaired person has a hearing problem, try to speak in a clear, pleasant voice. Speaking slowly and clearly will help.