The RNID (Royal National Institute For The Deaf) have an excellent website full of information and advice. Here’s a great example of their really useful content, some tips for communicating with a person who is deaf or who has hearing impairment.
People who are deaf or have hearing loss have individual communication needs and you should ask someone how best you can communicate with them. Not every tip below will be appropriate for every person who is deaf or has hearing loss.
Re-phrase what you said
If someone doesn’t understand you, repeat what you said or phrase it differently, use plain language.
Face the person you’re speaking to
Make sure you are facing the person you are talking to and speak clearly – avoid shouting, speaking too fast or unnecessarily slow.
Ask for the person’s communication preferences
Always ask what each person’s preferences are and if they need communication support. For example, even if someone’s using a hearing aid, ask if they need to lipread you.
Use an interpreter
You should always follow the advice of the person with communication needs. If that’s booking an interpreter or speaking to a friend or relative.
Write it down
Use pen on paper, text on device screens, or whiteboards to write what you want to say.
Get their full attention
Use simple gestures such as pointing or waving to get someone’s attention.
Reduce background noise
In a noisy place, move to a quieter area if possible.
Speak clearly and not too slowly. Use normal lip movements, facial expressions and gestures.
Find the right place
For longer chats, find a place to talk with good lighting, away from noise and distractions.
Speak at an appropriate volume
Keep your voice down: it’s uncomfortable for a hearing aid user if you shout, and it can look and feel aggressive.
Get to the point
Use plain language and don’t waffle.
Make it easy for people to lipread
Don’t cover your mouth when speaking. (If you’re wearing a mask, pull it down to speak but keep a distance).