We don’t know which ear can hear, how can hear, even if can hear the hearing impaired person, so talk to him/her always frontwise. Maybe touch him/her gently (!) and wait for eye contact. Don’t turn away later, keep the eye contact, moreover it is easier for them you understand if they can see your full body and body language.
It is needless to shout, over-articulate, use too simple sentences, but gabble is also not good.
For many hearing impaired person it is unpleasant ask back if they didn’t understand something. So, do it you, ask sometimes if they understand you. If not, don’t repeat the same word five times, try another synonym.
Don’t talk at the same time in a company, don’t eat, chewing gum, cover your mouth while talking.
Hearing damage means no way intellectual disability, don’t treat so deaf people. Communicate with them is not easy, but with little attention can be solved even as with able bodied people.