Remember that you are generally in control of the content you are presenting, so you can include topics that you want to talk about. Additionally, you can use personal examples from experience to support what you are saying. Since you are an authority on the topic, you want to speak with conviction like you really mean it. Your delivery will naturally be more conversational and spontaneous. Since you are not prepared with pages of notes, you are more likely to speak directly to the audience just like if you were speaking to another person in a conversation.