"Offer to God a sacrifice of thanksgiving, and fulfill your vows to the Most High."   -Psalm 50:14

What does God want from us? Singing? I guess that’s fine. Prayer? That’s OK too. Our attendance? Yes…
What He wants, first, is a thankful heart. Each one of us is to offer to Him the sacrifice of thanksgiving. A sacrifice is something which costs us. Have you ever asked yourself why the Scriptures stress thanksgiving so much? Both the Old and New Testaments emphasize that above everything else, God wants thankfulness.

"Give thanks in all circumstances, says the apostle Paul, for this is God's will for you in Christ Jesus."                                                                                                           - 1 Thessalonians 5:18

Why is this? It’s because thanksgiving only comes as a result of having received something. You don’t give thanks until you have received something that comes from someone else. Therefore thanksgiving is the proper expression of Christianity, because Christianity is receiving something constantly from God. Thanksgiving is the first thing He wants in worship.
The second thing is obedience. Fulfill your vows to the Most High. Notice the kind of obedience it is. It is not something forced upon you; it is something you have chosen for yourself. A vow is something you decide to give, a promise you make because of truth you have seen. You say, I never saw it like that before. I really ought to do something about it. God helping me, I'm going to do such and such. That is a vow. God says, I'm not asking you to do things you have not yet learned are important. But when you have vowed something, then do it. Act on it. Obey it. Our worship today comes from deep obedience and a heart of gratitude.