The key to expository preaching so that it doesn't become a college lecture is to remember your audience. There's a misnomer that unchurched people aren't interested in history or background. Not true. Christians aren' the only people who watch the history channel.
I am a firm believer in giving as much facts and data as you want… as long as it pushes the ball up the field. I don't share trivia for the sake of trivia. Instead, the background you give should give a basis for the application you give. Application without a theological foundation is just a glorified episode of Dr. Phil.
So remember your audience – the whole audience. That there are new believers, non-believers, and seasoned believers in the seats and we need to make sure our messages speak to all 3.