Assumed knowledge can be detrimental

Employees may have tunnel vision, new employees may not know, old employees may have forgotten.  Assumed knowledge can be detrimental. Re-communicate things that may seem obvious to you.  And avoid Acronyms. 

Few people 'get it' first time - especially if they feel ambushed

Where possible, start to communicate and  position the need for change prior to a 'Big Announcement'.  It may help employees move through the change curve faster.

Provide training and usage tips for communications channels

Provide training and guidance on the appropriate usage for the internal communications channels that you provide

Ensure Employees are ABLE to listen before you communicate

Think about timing, background noise, other priorities competing for their attention, relevance, attitude / are they receptive state for this type of message? (If relevant, where are they on the change curve?)

Communicating an Employee Value Proposition (EVP)

Regular and effective communication of your Employee Value Proposition  is just as important internally as it is externally (as long as you are delivering on it!)

Do your research and understand which incentives employees value...