I don’t remember where I picked up this little tip. I have read books and attended workshops on effective preaching. At this point in my life many of my friends are pastors and preachers but as a younger man I gave some time and attention to improving my craft. One piece of advice that would benefit any public speaker, it doesn’t have to be in the pulpit, is about effective illustrations. If you are going to use wiring in a light switch to make a point, make sure you know what you are talking about. There is probably at least one person in your audience, perhaps a professional electrician, that will know if your illustration is made poorly. If you are going to compare your topic to changing the oil in a car, planting a garden, sewing on a button, programming HTML or whatever might be helpful, make sure you are well informed if not an expert on the subject you use as a reference. Don’t assume no one will know the difference; someone will know if you say something wrong and then you will lose credibility. If they see you as poorly informed about building a bookcase, they may also lose confidence in your knowledge of the Bible (or whatever field you may be speaking to if it’s not the Bible). If you provide sloppy illustrations with erroneous information maybe you’re sloppy with your Bible study or lazy in sermon prep. As public speaking goes, teaching the Bible or preaching the Gospel needs to be done well.