A neat summary of some key ways to express yourself in a friendly, conversational tone here on a post from Pick The Brain.
All too often, writing on behalf of an organisation seems to disengage the normal part of the brain that people usually rely on to communicate and instead adds some kind of 'quasi-formality loop'.
The article discusses the research in the book 'eLearning and the Science of Instruction' that shows that there are real learning gains to be made in addressing learners in a way that reflects conversation - in effect 'tricking' the brain in to thinking that it is part of a conversation which is an activity that we somehow rate as more valuable, hence more memorable, than simply reading.
Since we all know how to talk, ensuring that we use a more relaxed tone in addressing learners is, in effect, a free benefit. Great stuff.