Here’s a talk by Carl Trueman on preaching. You should listen to it. I think you’ll be helped.
If I were to start transcribing it, I’d probably end up tempted to do the whole thing. Here’s a taste. Trueman thinks that the story of the thief on the cross is a great example of the meaning of relevance. After summarizing several interesting and sound points, he adds:
What is relevant? I’ll tell you what is relevant: preparing people to die. That is the ultimately, the only real, relevant thing that a pastor does. Everything else may have passing relevance, but the only thing of eternal relevance is preparing people to die. I think if you hold that in your mind, that will give you a sober assessment of what is and is not relevant.