The Mass has the same shape everywhere in the world. Once you can see the shape, you stop watching for cues and start praying it.
The Mass is two things joined together, with a short opening and a short ending on either side.
The Liturgy of the Word. We listen to Scripture and to the homily. God speaks to us first.
The Liturgy of the Eucharist. Bread and wine are brought forward, the great prayer of thanksgiving is prayed over them, and Communion is given.
The Church teaches that in the Eucharist the bread and wine become the Body and Blood of Christ. This is why the Mass is the center of Catholic life: Christ Himself is at the center of it.
That order is very old. It is the same order as the road to Emmaus in Luke 24: first He opens the Scriptures to them, then He breaks bread, and only then do they recognize Him.
Red says what is happening. Below it, what you do.
Everyone stands and sings as the priest comes in. If you can arrive a few minutes early, kneel first and tell God why you came.
The Sign of the Cross, then the first of the exchanges you will hear throughout.
We acknowledge our sins together and ask for mercy before we go any further. It takes a minute. Mean it.
The Gloria is sung on Sundays outside Advent and Lent. Then a short prayer that gathers everyone's intentions together.
Sit. Usually an Old Testament reading, then a psalm everyone answers, then a New Testament letter. Listen rather than read along if you can; these were written to be heard.
Everyone stands, because we are about to hear the words of Christ Himself.
You will see people trace a small cross on the forehead, the lips, and the heart. It is a way of asking that His word be on our minds, on our lips, and in our hearts.
Sit. Take one thing from it. One is enough.
Stand. The Creed on Sundays, then prayers for the Church, the world, the sick and the dead. Add your own quietly.
Sit. The bread, the wine and the collection are brought forward. Many people quietly place something of their own week on the altar at this point: a person, a worry, a decision.
Stand for the opening exchange and the Holy, Holy, Holy, then kneel.
This is the heart of the Mass. The priest prays the words Christ spoke at the Last Supper, and the Church teaches that the bread and wine become His Body and Blood. We kneel because of what is happening on the altar.
Stand for the Our Father. Then turn to the people near you and wish them peace, and mean that too. Then a short litany while the bread is broken.
See part five below. Afterward there is a stretch of silence. It is the most valuable silence of your week.
Stand. A blessing, and then we are sent out. The word "Mass" comes from that sending. It does not mean "you may now leave." It means go and live what you have received.
Each posture means something. Standing is respect and readiness. Sitting is listening. Kneeling is worship.
These vary somewhat from one diocese and parish to another. If you are unsure, simply do what the people around you are doing. That is not cheating. It is how everyone learned.
Two smaller customs: genuflect, briefly touching your right knee to the floor, toward the tabernacle before entering your pew; and bow your head before receiving Communion.
The priest's line is in italics; yours follows. There are about a dozen, and you will have them within a month.
That second-to-last response is worth knowing. It comes from the Roman centurion in Matthew 8, a man who was not a Jew, who asked Jesus for a healing he did not think himself entitled to, and whom Jesus praised for having greater faith than anyone in Israel.
Rows go up in turn. Follow the people in front of you.
When you reach the front, bow your head. Then either place your left hand over your right to receive in the hand, or open your mouth to receive on the tongue. Both are permitted.
The minister says "The Body of Christ." You answer "Amen" out loud, and consume it there before you turn to walk back. Then return to your pew, kneel, and pray.
The Church asks that we receive Communion in a state of grace, and that anyone conscious of grave sin go to Confession first. This is not a punishment; it is what it means to take the Eucharist seriously.
So do not receive if:
In many parishes it is common to go up anyway with your arms crossed over your chest, and the priest will give a blessing instead. That is a widespread custom rather than something guaranteed everywhere, so if you would rather simply stay in your pew, that is perfectly fine too. Nobody is watching you as closely as you think.
The Church asks that we take nothing but water and medicine for one hour before receiving. Most people meet this without trying.
Find a Mass that fits your week. masstimes.org lists Mass times for parishes across the country, including Saturday evening and Sunday evening, which many people do not realize fulfill the Sunday obligation. It is also the thing to use when you are away from home.
Read the Gospel before you go. Ten minutes on Saturday night, and Sunday stops being the first time you have met the passage.
Arrive a few minutes early. The difference between sliding in during the entrance hymn and sitting quietly beforehand is larger than a few minutes should account for.
Bring one thing to put on the altar. A person, a decision, something you are afraid of. Offer it during the preparation of the gifts.
Expect to be distracted. Everyone is, every week. Noticing and coming back is the same work as on the beads, and it is not a sign you are doing it badly.
The Eucharist is the source and summit of the Christian life. Second Vatican Council, Lumen Gentium 11