Internal Memo features:

• clear purpose, clear content
  
• problem clearly identified, solution clearly presented 
• often front loading is best
  
• What does this mean to me?
• not a taxing length
  
• focused, legitimate audience
  
• professional tone
• avoid emotionally charged words (or use them meaningfully)
• first person is good for personal communication 
• proper relationship between sender and receiver
  
• formatting
• emphasis, bullets
• breaking into chunks (with headers if necessary)
• mechanics (EAE)