Outdoor preaching is more common in the UK and Irish Republic than in the US. And, it is not just the odd fundamentalists who do it. When my wife was part of a Free Church of Scotland (continuing) congregation in Glasgow, their pastor and members did open air evangelism on the streets at least every two weeks. I have friends who do the same in Northern Ireland and London. Of course, there, one is more likely to encounter opposition and hecklers than here.
When two of my British friends were visiting Boise earlier this year, we went to the University (BSU) to do open air witnessing and preaching. I regarded it as an opportunity to learn from these experienced open air preachers. Standing on a concrete bench beside the main walkway through campus, we proclaimed the gospel as people crossed the campus.
Things I learned: 1) Several preachers preaching short sermons are better than one. Your voice will hold out for only a short time if you speak any louder than a normal preaching voice. 2) You need at least a couple people with you to provide a constant audience. These standing and listening help you to focus and may induce others to stop. These should not be talking to pedestrians while you preach, but listening. They might extend a tract to those passing. 3) You don’t preach the same sort of sermon you do for public worship. You are addressing people who know little about the Bible and hold pagan philosophies. Paul’s sermon in Athens (Acts 17) is a great example of addressing such an audience. Speak of the Creator who may do what he wills with his creatures, who is not obligated to be “fair” in our contemporary understanding that word but is “just” in his condemnation of sin, who has provided one to bear the guilt and penalty for our sins, an exclusive savior. Such a message will possibly provoke discussion and challenge the philosophies and assumptions of many people today. 4) Figure most of those passing by will only hear sixty to ninety seconds of your message from the time they come into hearing and then pass beyond. Your points need to be short, such to provoke thought and perhaps induce some to stop and listen to more. 5) If one is there on a regular basis, each message reinforces the previous ones. 6) Be ready to deal with hecklers. My British friends were good at this. A lively exchange may cause others to stop. 7) Pass out tracts in between preachers and expect a few individuals to engage you in longer discussions.
I’d recommend developing a team of at least three persons to do outdoor evangelism and preaching together. Find the right spot or spots; and return on a regular basis. Reformed folk should be doing this more often and not leaving it to bizarre fundamentalists.