I don't often do "how to write" posts, because there are many other authors that do it so much better. However, I do notice that a lot of people are trying to more inclusive with representation in their stories, and I think that's a great thing. Writing inclusively means that the author gets the opportunity to learn about other people, which quite often leads to a more empathetic understanding of one another.
A lot of people will say "I'm not your Google." I rarely say that, because algorithms are based on a person's search history, and if someone is deft at wading through the mass of online information, this usually isn't a problem. However, given the number of "informative" faux sites that are little more than opinions disguised as information, I'm usually okay-dokey with pointing people to good resources.
Occupational hazard, I guess.
So if you're thinking of placing a deaf character in your stories, this might be the right post for you. I'll give you a few hints based on my own experience, which may or may not be the same as others. Hearing losses are variable and people have different coping mechanisms, depending on the type of loss that they experience.
As the author, you will have to spend time learning about hearing loss. You can do this by speaking to an audiologist. The reason I suggest an audiologist rather than someone who is deaf is because the audiologist will be able to give you a broad overview of the types of hearing loss, and how each different type affects the person's life. Once you know what kind of hearing loss you want to represent in your story, then is the time to contact an individual with that type of hearing loss.
What type of hearing loss does your character have? Is it conductive, sensorineural, or mixed? Each type of loss will affect hearing differently, and this, in turn, will affect your character's lifestyle and ability to communicate.
How badly does the hearing loss affect speech discrimination? Speech discrimination is quite simply an individual's ability to understand the spoken word. If your speech discrimination is one hundred percent, you can understand every word someone speaks. People with hearing loss will have a much lower percentage of speech discrimination and will have to make communication adjustments, which I will cover below.
What ranges can the person hear? Can your character hear high pitches, or only low tones? Knowing what they can hear will easily direct you to what they cannot hear.
So when you're writing a deaf character, you need to establish the individual's level of hearing from the beginning of the story. Even if you never tell the reader all of these things, the author must know how the deaf person will interact with the outside world.
For example: I have lost the higher ranges and can only hear a few of the lower pitches. So when I'm in a crowd, the noise is a lot like rushing water or a meaningless roar. Individual sounds are lost to me. Also, I don't know how it is for other deaf people, but quite often, I can't tell the direction of loud sounds. When out in the public, I am hyper-aware of my surroundings and other people, because I derive my cues from hearing people.
Lip reading. Some people tend to think that lip reading is easy. It's not. I do it exceptionally well, it's sort of like my superpower, because I've been lip reading since I was twelve. Not many people can lip read to perfection, or at least no one I know can do it. Hearing is as dependent on the brain as it is on the ears. Sound goes into the ears and the brain tells us how to interpret that sound.
Enunciation is the key. That, and it takes a lot of focus and energy on the deaf person's part. I have to associate a person's lip movement with the sounds that I can hear, and (going back to pitches and the tones I can hear) that will differ from one person to the next. Sometimes I can't understand someone at all until we've communicated for a few minutes. The longer they talk, the easier it is for me to connect their words with their lip movements. I may pick up 8% of the words being said and fill in the rest through context.
There are a lot of mental gymnastics that go into lip reading, and those can make a person tired. I have to take breaks during long conversations. Also during events like conventions, it's terribly difficult to go from one panel to another with no breaks. I tend to shut down in the evenings by reading books or writing, which doesn't require the same focus as communication.
Hearing aids and cochlear implants. Devices are great, and there are a great variety on the market today. Just remember: hearing aids are not hearing miracles. Hearing aids assist a deaf person by raising the sound level, and there are many different devices on the market today. Cochlear implants work in a completely different way. Some people use neither, others use a combination of hearing aid and implant. Again, this will vary depending on the type and range of hearing loss.
Sign language. Not everyone who is deaf understands sign language, and not everyone who understands sign language can understand sign language by people from other countries. Even in America, American Sign Language (ASL) will have regional variations. Black American Sign Language is a different dialect of ASL that developed during segregation. While the American Sign Language system is based on the French system imported to America by Thomas Hopkins Gallaudet and his French teacher, Laurent Clerc, it is not a universal language.
Body language. Deaf people are usually able to read body language much better than hearing people. Even from a distance, I can usually detect subtle forms of body language that can cue to me to the tone of a conversation between two people. That is why in my stories, you will find many references to my characters and their body language.
When searching for sources, look for .org websites. Here are two to start you off if you're in the U.S.