Jesus sent out these twelve after instructing them thus, "Do not go into pagan territory or enter a Samaritan town. Go rather to the lost sheep of the house of Israel."
The most effective evangelization is done from a place of love. It also helps if the people you are sharing the Gospel have some kind of pre-existing connection with you; some common ground. In these verses, Jesus commissions the Twelve to proclaim the Kingdom to Jews like themselves. These would be people who whose customs they would be intimately familiar with, whose language they shared, and who already worshipped the same God. This approach can be extremely helpful for us too. In sharing Jesus, look for those things you already share in common with the ones you are evangelizing. Let these similarities be the foundation through with you can introduce someone to Christ, and always do so out of love.