One common, but difficult type of introduction is the use of humor. Not only is humor difficult to handle well, it frequently has no relation, or only a forced relation, to the theme. Even more dangerous, not all of the hearers may see the humor. The opening sentence should be addressed to the mind. The development of the introduction should be addressed to the heart.
Failure here results in preaching just on a subject, rather than to living, feeling, needy people.
The transition from the introduction to the body stirs curiosity by promising something. The sermon must deliver whatever the transition promises, or the preacher loses credibility. The way some sermons begin, the hearers expect the preacher to descend from the pulpit with tables of stone. At the very least they expect lightning to flash and thunder to roll. The introduction should never belittle the hearers.