If you’re fearful about preaching open-air for the first time, practice at home before doing it “live.” Go over the gospel in your mind until it’s second nature—no, until it’s first nature. When you are alone, preach it. (In the shower is a great place to preach.) Go through a few anecdotes. Get used to the sound of your own voice. Pretend to engage a heckler. Invite some friends over to role-play with you—and practice what you preach.
If you are afraid of looking foolish if you mentally draw a blank while speaking, have a backup plan. Keep a New Testament with you and if you freeze up, say, “I would just like to read something to you.” Read John 3:16–18 and conclude with, “Thank you for listening.” Just knowing that you have that option will dissipate the fear.