“A simple and conversational, yet forceful delivery commands both respect and response. Enthusiasm inspires. Logic is convincing, the illogical confusing. As preachers let us have a heart. Let us stop wearying our audiences. Let us make our preaching so absorbingly interesting that even the children would rather listen to us than draw pictures and will thus put to shame their paper-and-pencil-supplying parents. But we may as well make up our minds that an absolute prerequisite of such preaching is the most painstaking preparation.”
You can read his five CAUTIONS concerning expository preaching here.