5. Don't Think About The Audience You Are Speaking To
I may be slow. It took me a couple years to realize that I'm not just preaching about the Bible, I'm preaching about the Bible to people. I came out of seminary with the attitude (almost) that the way I would preach to a wall would be the same way I would preach to a group of people, and though I don't have chapter and verse on this one, six years later I think that's pretty dumb.
For one thing, it's not the way I work outside the pulpit. When I try to explain something to my five year old daughter, I do it a little differently than if I were trying to explain it to a sixteen year old. Essentially, what I'm saying might be the same - but how I go about saying it probably will be a little bit different. If I'm really going to expect my five year old daughter to understand me, I can't just think about what I'm going to tell her, I have to work on the way I'm going to tell her.
That's part of being unselfish. I'm concerned about the other person and because I'm concerned about the other person, I think about how I can help them understand what I'm saying - realizing there is a good likelihood that they are different than me.
Bruce Wilhite describes what I'm talking about here as thinking about your sermon from the pew's perspective. Look at what you are saying and think about it from the perspective of different people within the congregation. The point is not to change the content, but to think about the best way to communicate it.