This is designed for youth groups where the majority are Christian and are for the most part timid when it comes to evangelizing.
Have the youth get into pairs. One person is person “A” and the other is person “B”. “A” then is instructed to witness to “B”, that is, to explain what it means to be a Christian or why “A” decided to be a Christian. After “A” is finished, “B” will do the same thing to “A”. You can share some of the answers that were given. Then have all the “A”‘s stand to one side and the “B”‘s to the other. Explain that “A” is going to persuade “B” (pretending to be non-Christian) to become a Christian. “B” can respond positively or negatively. “B” might be very open or “B” might be closed, but “B” at least should be open to hearing what “A” has to say. While giving “A” a couple of minutes to think of what they will say, ask “B” to try to think of a couple of questions for “A”, that is, questions about problems they have with Christianity. Ask them to base it on excuses people give for not accepting Christianity. Then let “B” and “A” go for it; “A” persuading and “B” maybe asking questions.
After a few minutes, get some feedback; what worked, what didn’t, did anyone convert, what could work better? Then divide “B”‘s and “A”‘s again, this time having the “B”‘s evangelizing the “A”‘s.
Since the group probably knows each other well, they will probably feel more comfortable doing this with each other. From the results of this exercise, you can decided what the next step is to getting them excited about sharing the Good News with friends, family, and strangers.