If you live a Christian life and if you love others, it will not be hidden. That is the best type of witness given. As one hymn puts it: "They will know we are Christians by our love, by our love. Yes, they will know we are Christians by our love." Contrived and memorized presentations and hitting people over the head with a Bible, rather than spontaneous sharing can often drive people away from Jesus. This is what Jesus states to his disciples: "You are the light of the world. A city on a hill cannot be hidden. Neither do people light a lamp and put it under a bowl. Instead they put in on its stand, and it gives light to eeryone in the house. In the same way, let your light shine before men, that they may see your GOOD DEEDS and praise your Father in heaven." The best sermon, the best preaching is your Christian life.
Matt. 5:14-16
If you "walk the walk", you will also have opportunities to "talk the talk."