As you build your sphere of influence, you may connect with the deaf or hard of hearing. If you don't know how to communicate with them, you may strain the relationship through etiquette blunders or even just inefficiency. Always ask them how they prefer to communicate, but start with these guidelines from Lifehacker.com and you'll quickly pick up the rest.
To get their attention, a few options include moving into their field of vision, gently tapping on their shoulder, or flicking the lights at a slow or medium pace. (Faster may indicate an emergency.) The first option is best because it immediately creates eye contact. But be aware that you may be interrupting them; ask whether that's the case and wait your turn if so.
Once you're in a conversation, let them take the lead. Not all deaf people can read lips, so have writing materials ready if they prefer to use those. If they prefer to lip-read, stay visible and in good lighting. Speak a bit slower than normally, but don't exaggerate lip movements or overenunciate. Keep in mind that they can be distracted just as you are; give them a moment to understand and confirm with them that they do.
Gestures and body language can bring useful context to your words, so don't be afraid to use them. Again, don't overdo your movements, but think of ways to convey your points.
Finally, ask them if they can teach you a few signs to help you talk or work with them. Your sincere effort on this part can help you start to build a vocabulary that will make future discussions, with them and other deaf and hard-of-hearing people, easier.
Source: "How to Communicate With Deaf People When You Don't Know Sign Language," Lifehacker.com (Oct. 17, 2017)