Action Deafness has produced some really neat posters that speak volumes for deaf people. They can be purchased as A3 sheets from Action Deafness online shop. Having these posters around can remind people about their speaking behaviours in the same way as places have safety posters.
A related article in Metro gives advice in the form of 12 tips on talking to people with hearing loss. They include speaking as you would to anyone else, but there are some don’ts in the list such as: don’t assume they know you are talking to them, and don’t waffle.