1. What do I want to communicate? If you can’t simply summarize in a sentence or two what you want to communicate, you probably are unclear yourself. I've heard it said that mist in the pulpit creates fog in the pew. You must know and understand what is the big idea of the message you are trying to communicate.
2. Why should the recipient care? In any communication, it should be clear in the beginning (not by the end) why the recipient should read/listen/watch – they’re thinking “what’s in it for me?” Just because you are passionate about something, doesn't mean your audience is going to be. Make a connection, and help them to see why this matters to them.
3. Am I boring? Be creative in how you communicate. Don't just lay out boring facts. Tell a story. Use an illustration. Play a video. Are their memorable ways you can make your message stick?
4. What has the potential to provide confusion? - Try to put yourself in the listeners shoes. Don't assume your audience knows what you know, and therefore your assumptions might lend to their confusion.
5. What do I want the recipient to do? Is it to Give, Pray, Come, Serve, Sign-up, Invite Others, Consider, Attend? What is it that you want them to do? What is your action point? If you are unclear, it is certain they will be too.
(thanks to Communicate Jesus for some thoughts on the subject)