Now to it.
Humility is the most important thing in the world, and therefore it is the most important thing in preaching. The preacher must be humble. There is nothing less tolerable and more awkward than an arrogant preacher. Oh, let me guess, you're the hero of this story, too? Ah, another personal illustration of how godly you are! Let me give you some practical advice: Never tell a story that makes you look good.
You need to understand that the congregation assumes, simply by the mere fact that you are preaching, that you are more mature, more spiritual, and just plain better than they are. They expect you to have wisdom they need. They anticipate that you will say something that will change their lives. They are willing to sit, in silence, and listen to you talk without interruption for up to an hour. You, preacher, are highly-esteemed and wield a power that is unparalleled by any other vocation in our soundbite, jump cut, 140-character tweet culture. If you do not come to the task with humility, therefore, it will swallow you whole.
The preacher's responsibility is to step down from the pedestal upon which he has been placed by the congregation. God, alone, can be lifted up. You cannot take his place. If you stand too tall you will block the congregation's view of the risen Christ. So how can a preacher stay humble?
Don't Take Yourself Too Seriously
Your task is important, but you are not. Don't get caught up thinking that you're going to save the world through your preaching. That's ridiculous. God's going to save the world through his Son, you just get to talk about him.
Make fun of yourself. Be open about your shortcomings. Tell stories about how you've gotten it wrong. Name your sin before the congregation. Too many preachers think they have to maintain some kind of image in the society of their church, but that kind of image is from the devil. The only image you need to maintain is the broken-but-being-repaired image of God you carry with you everywhere.
If you're going to share a personal illustration, make sure it's one where someone else in your church comes out looking good. Heap praise on other staff members. If you share a pulpit, talk up the other preachers on your team. And, most importantly, mean it.
Be Respectful of Opposing Viewpoints
Who knows, but maybe you're not nearly as right as you think you are. Don't let arrogance seep out of your soul by trashing someone else's viewpoint (or, even worse, someone else's humanity). Talk about it as though you were having a respectful dialogue with someone with whom you're trying to share Jesus.
I'm sure there are other things we could do to demonstrate humility in the pulpit. Maybe you've seen a good or bad example of this: please leave it in the comments so we can all learn. Remember, whether you're a preacher or a CEO or a college student, humility is the most important thing in the world.