- Look for opportunities - always be alert for what might turn out to be a Divine appointment.
- Don't give too much information - You don't need to talk about evolution, young/old earth, eschatology, prophecy, Darwinism, pretribulation rapture, amillenialism to be effective. The gospel is plenty enough for a non believer to get their head around.
- Stay away from religious language, terminology, affectations - speak in language that the person can understand. People might be interested in Christ before they are interested in Christian religion.
- Focus on the truth, not personal benefits of Christianity - It doesn't matter what people like or don't like, examine the truth claims of Christianity, not the promises of personal benefits.
- Give evidence - Everyone else in the Bible did as well. Give the scripture evidence for what you are witnessing to people. People do respond to that, even in a post modern age.
- Stay calm - don't get crazy or frustrated. The more calm you stay, the more confident you look, the more persuasive you sound.
- Let them walk away - When someone is finished with the conversation looking for a way out. Let them go. They are not listening anymore. "Don't bruise the fruit."
- Leave them with something - The gospel of John, or a clear gospel tract is a great way to give them more to do after you are gone. If they read the bible, Jesus can speak for Himself. Give them some way to make the next step.
Adapted from the Stand to Reason podcast with Greg Koukl