The ordinary means of someone becoming a good doctor that can diagnose your illness and hopefully offer a cure is that they went to some kind of competent medical school and learned how to be a good doctor. This is not to say that God could not have extra ordinarily imparted some skill or understanding to a person who never went through that process, however ordinarily God works through ordinary means.
It is the same with Christianity. Ordinary God uses the preaching of the Word, and in particular the law and the gospel to bring someone to see they are a sinner who needs a savior, and then Christ is offered as that savior as we find in the scriptures.
God continues to use this ordinary means of grace to not only create faith (which is the instrument that God has ordained that takes hold of Christ and His salvation and benefits), but to grow, mature and strengthen the faith of that believer over their lifetime. Which has an effect of their preservation to glory (1Pet 1:5) but also love and good works freely done from the heart (Rom 6:17), and glorification of God with one’s life.
Not only does the Word of God (particularly the clearly and accurately proclaimed gospel) taught and proclaimed weekly bring these things about, but there is also a physical, and material means God has provided of His covenant love for us (Lk 22:20).
These are the sacraments, which are signs and seals of the covenant of grace (Rom 4:11). Whereas baptism is a type of covenant initiation ceremony (think of a wedding with a vow from God and a ring that we are his forever!) and the supper as a covenant renewal ceremony (think of a wedding anniversary where He again proclaims his love for us that we are his forever!) where Christ renews us, nourishing and sustaining our souls in the heavenlies where we are with him and also here in time in this world.
These ordinary means of grace are the gifts of God to us, and so on Sunday we must make use of these means God has ordained. To the extent that these things are diminished, or that the gospel is not clearly or less purely proclaimed, or the sacraments not rightly distributed. This visible church becomes less visible, and has a less bright lampstand, because the truth that the Spirit of God ordians to create strenghten and increase faith was not faithfully administered and proclaimed.
However, words fail me as to the amazing results of the rightly handeled ordinary (and weak looking to the world) means of grace. New creations come into existence. Eternal life is born. Growth, maturity, changed hearts, the weak are made strong, the brokenhearted healed. God uses what looks weak and foolish to the world to much greater power and effect than mans best can provide. Christian, God loves you, and saves you. He has ordained that no one will snatch you from His hand!
John 10:27 My sheep hear my voice, and I know them, and they follow me. 28 I give them eternal life, and they will never perish, and no one will snatch them out of my hand. 29 My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. 30 I and the Father are one.”