What possible problems might a speaker encounter when using humor in a speech introduction? Can such problems be prevented? What are some suggestions for dealing with humor and its appropriateness?

One option for concluding a speech is through the use of an appeal, which can be emotional or based on cost/reward. What are the ethical implications of appealing to an audience at the end of a speech? What must a speaker do, in both the speech's content and delivery, to successfully appeal to an audience, and stay within ethical boundaries?

Which is more difficult for the speaker, the introduction or conclusion? Why? What, if anything, can be done to make it easier?