Use appropriate knowledge level and language for each customer. Avoid jargon and techno-speak. You might think that “blinding ‘em with science” makes you look clever, but all it does is make you look like a dick.
Use an appropriate communication channel for the customer – do they prefer to communicate with you via phone, email, letter or face-to-face/personal?
Be clear, concise, and to the point
Make communications convenient (e.g. what’s the best time to phone?)
Be friendly and approachable.
Listen to what the customer is REALLY saying – you have 2 ears and 1 mouth – use them in that ratio.
Check your spellings and grammar – be professional.
Make it clear why you’re communicating and what about
Have a consistent message.