We usually overestimate our ability to communicate and this can even be magnified when the communication is with people who we know well. Often because we believe we have a deeper level of understanding than is actually the case.
We should try to speak to people as individuals even when they are in groups. Do not allow yourself to be distracted and focus on delivering your message in a genuine way with both enthusiasm and energy.
Knowing the Subject Matter is Essential
You really do need to know the subject, this is a fundamental part of establishing rapport and respect with you audience (both of which are essential for effective communication).
Pay particular attention to your audience and strive to build the connection, adjust your message so that it resonates with the audience, focus on getting your message across without overdoing, seek questions as a way of ensuring the message is received.