When Paul tells us in Romans 12:1-2 to present our bodies as living sacrifices, he is instructing us about a proper approach to worship. By worship, I mean the corporate gathering of the people of God, not our private moments with God. When we gather as the people of God, as many of us will do this morning, we are called by God to present ourselves as living sacrifices, and that is the kind of worship/service (a priestly word in our passage) that will be pleasing to him.
What does that mean? Well, at least on one level it means that worship takes work. For the priest to offer a sacrifice, it meant a great deal of work on his part. So also with us. We come before the Lord to sing his praise, and confess our sin and hear his promise of forgiveness. We come before the Lord to confess our faith and hear his word. And it takes work and practice to do this together as the people of God. We should sing vibrantly; we should respond joyfully and clearly in corporate prayers and readings. We should be engage throughout the worship service. We should have attentive ears as the minister preaches the Word. We should participate in communion as if we have been lifted up into heaven to sit with Christ because indeed, that is where we are by faith. And we should leave with the blessing of God knowing that we are going out into this world as salt and light. In our culture, all of these issues take practice and patience. May the Lord give us the grace to lean against our cultural trends and present ourselves as living sacrifices to him.
UPDATE: To clarify what I am talking about concerning worship, especially the idea of leaning against our cultural sins, see here.