One tip for communication is to make sure the HOH person knows what the general topic of discussion is before getting into details.
Two issues here. First, even the best lip readers can only understand around 40% of conversations. One obstacle is that some sounds look the same on the lips, such as m and b.
Second, many HOH people need a higher signal to noise ratio then the normal hearing. This means that the speech needs to be a lot louder than the background noise before it can be understood.