Being clear is as important when speaking as it is when writing. Whether you are speaking or writing your message, be brief, be clear, and consider the background knowledge of your audience.
Whatever sector you work in, I urge you to check out this fine example of clear communication and participatory design. Why? Because good work is contagious.
Sarah Carr has written a concise yet comprehensive guide to communicating with older people that succeeds in offering practical advice without ever coming across as patronizing.