You have a text, maybe more, but certainly one. You study it. You determine what it’s purpose was and the author’s idea. Then you consider your congregation and the purpose of preaching the sermon. You shape the idea, then the sermon and preach. Simple really. But there are some traps we easily fall into. Here are a couple to consider:
Don’t Overqualify. Often the text will be saying something quite strong. We want to make sure we’re not misunderstood or somehow imbalanced, so we qualify it. This text says this. But don’t forget that other text that says that, and the other that says something else. Before we know it, we’ve overqualified the message and the force of the sermon has been dissipated like replacing a bullet with two dozen marshmallows. There are times when we must communicate careful balancing of a potentially misunderstandable idea. Generally though, don’t overqualify a message and end up saying nothing. A lot of balancing can come through future preaching of other texts.
Don’t Overteach. It’s easy to cram a perfectly good message with extra information that would be best suited in perfectly good other messages. Either we can try to dump every scrap of exegetical inquiry into the message, or we can cram too many ideas into a one-idea time slot. “Seven great lessons from the book of whatever” would generally be more effective as seven separate sermons. Once the ideas start to pile up, people will either synthesize the message in their own way (over which you have no real influence), or they will take one “nugget” and ignore the rest (and that nugget may be a merely anecdotal illustration), or they will simply take away nothing. Generally speaking, don’t overteach in a message so that in saying lots, people actually take home little to nothing.
Don’t try to say everything. Don’t try to say lots of things. Don’t risk the people getting nothing. Say something. Say the something the text pushes you towards. Say the text’s something and try to say it well.