It occurred to me while writing the previous post: really we are instructed to preach the gospel in two manners: a) active; and b) reactive. Where active is drawn from Mark 16:15, an instruction to put a foot forward, to tell people without any prompting. Alternatively reactive is drawn from 1 Peter 3:14-15 to be ready to answer questions whenever they are asked.
After some more consideration I have decided it is a little more complex: when answering a question we are instructed to do so wisely. Often when someone asks a question it will not be: How can I be saved? So we should not treat peoples questions as a general preaching of the gospel, we should answer the question and tailor our response to the individual. When actively preaching there is no question. Two different witnessing styles are required.
I’m not really a fan for stopping someone in the street and suggesting they must repent or burn: often that will get a response like: Get away from me you crazy person!!! I would suggest the best way to witness in an active mode is to bait your conversation. Tell people what you are doing in the church or what you got out of the talk on Sunday (or whenever). Lead the conversation in a manner that they really need to ask: What does that mean? Of course there are some environments where you really will just need to speak the gospel but we should all be capable of discerning those times.