Points to aid communication with people who are deaf or hard  of hearing:

Make sure your are in facing the person and are on the same level.
Make sure your face is lit. Do not stand with your back to the window.
Try to cut out background noise - go somewhere else if necessary to communicate important issues.
Do not shout. This means you must certainly not screech. However if your voice is naturally quiet then you may need to make an effort to project a bit more.
Speak clearly, use a normal rhythm of speech
Sentences and phrases are easier to understand than isolated words
If something is not understood then rephrase it (put it a different way) but never ever say "Oh - it doesn't matter".
Allow more time for the person to absorb what has been said.
Keep your head still - or stop talking if you turn away.
Keep your hands away from your mouth
No smoking
No eating
Do not exaggerate facial movement or grimace
Gesture a little if appropriate but not too much
Check for understanding
Write things down if necessary
Avoid lipstick unless the person is also visually impaired
Beards and moustaches make it more difficult
Lip-reading and listening through a hearing aid is very tiring.

Georgette Vale SNAG 2009