You never know where a random act of kindness will lead. You never know who is watching. You never know when it will be you on the receiving end of a kind act. Most of all, it is how Jesus lived.
Preach absolutely, but let it be more than words. Let the good deeds prove that the faith you proclaim is genuine and the kind acts show that the person is more than a conversion quota but a human being who bears the Imago Dei, the image of God.