I think a marriage ceremony best illustrates what I am trying to say happens in the ritual called baptism. What happens at a wedding? A man and a woman come together before witnesses. They exchange vows and make commitments. They publicly state their intention to be husband and wife. They enter into an institution which is very old and honored in most cultures.
Well, there you have it. Have they been changed? Yes. They are now legally a partnership. There is a moral expectation that they will forsake all others and be faithful to one another. Can a newly maried person go out that night and "party" with someone else. Yes. Do the vows make the love perfect? No. But there is a difference between someone who is in a vowed life and someone who is not. How often have we heard about couples who live together but do not want to get married because it will "ruin" the relationship. Obviously such people believe that marriage is real and does something. Even a sham marriage is still observably different than a non-marriage.
When people sincerely seek to be a married couple then the activity of the ritual does in fact increase and intensify the relationship. That is why people, including very often the groom, get emotional at a wedding. There is something real taking place. But it is not magic which makes relationship suddenly easy. There is still a struggle.
What is God doing in a marriage? Well from my view point He uses marriage to teach us to love. Love is something we are not very good at much of the time. There is a reason why half of marriages end in divorce. Most of us are looking to get something. Marriage is a symbol of giving. But BOTH parties must give or it will not work. Marriage is a sign of Jesus' love for the church. Jesus, the groom, marries the church, the bride. Baptism is our entry into that relationship.
The way God shapes and forms us is slow. The ritual marks the beginning of the process. Just like birth changes everything, but the process still continues. Is God active in weddings? We invite Him to be, I guess no one can prove He is, but neither can one prove He isn't. I do know this, if we have eyes to see then we can discern Him there. I know that if our expectations and assumptions are rightly ordered to reflect the real world and not our own desires I think we will see God more clearly. Unfortunately, I think much of the time my wishes and fantasies make that harder for me than it needs to be. But in the end, if we can see how a wedding ceremony does make something happen, perhaps we can also see how baptism does the same.