As the Liturgy of the Word begins, we sit for the first time. First of all sitting is the common posture of all gathered so it shows our unity. Secondly, sitting is a posture of being receptive. Hopefully we know we are being receptive to Jesus himself in the Word proclaimed. God is speaking to His people and we are receiving spiritual nourishment.
The Second Vatican Ecumenical Council reminds us that we are not passive spectators at the Holy Sacrifice of the Mass. All the faithful are called to full and active participation. Sometimes the word "active" is translated as "actual." In the Liturgy of the Word, we participate well through active listening.
It should also me pointed out that the person who gets up to proclaim the sacred text does not participate more or better by doing this task. All the faithful are capable of participating fully from the pews.
At the end of the reading, we reply, "Thanks be to God." This shows our unity in thanksgiving. Our thanksgiving will build until its climax in the Eucharistic Prayer which it self is a prayer of thanksgiving acknowledging the "Good Gift" (eu-charis in Greek). The General Instruction of the Roman Missal (GIRM) says the faithful are "honoring the Word of God they have received in faith and with grateful hearts."
A period of silence after each reading and the homily is good for enhancing meditation. The GIRM says: "By their silence and singing, the people make God's Word their own." This singing happens during the Responsorial Psalm which is also Sacred Scripture and thus cannot be substituted for some other poem or literature. A person waiting to read the second reading should never be standing and waiting, but joining all the faithful in the seated position of being receptive to the Lord. Singing shows our unity in faith as we sing with one voice. It also fosters meditation and praises God. I think it was St. Augustine who said, "He who sings prays twice."
There are many non-verbals associated with the proclamation of the Gospel at Holy Mass. This shows its elevation from all other texts because it is the life of Jesus our Blessed Lord and His very words. First we stand because we are meeting our Blessed Lord in His words. We always stand to greet someone. As we stand we sing the Gospel acclamations, Alleluias at this time of year. This shows we are praising God who is about to speak to us in the Gospel. The Gospel has its own book, known also as the evangelary. Perhaps this could remind us we are hearing the words of Christ who is God in human flesh. The Gospel has to be proclaimed at Mass by an ordained minister. This shows it is the high point of the Liturgy of the Word. That ordained minister can also incense the book of the Gospels as it is open to the page. We incense things that are holy. It is certainly holy as it contains the words of Jesus himself. Many regions have adopted the gesture of making three crosses, one each on the forehead, lips, and breast. Some will even pray to the Lord: "May your Word be on my mind, on my lips and in my heart" as a sign to continually meditate on it, share it with the world, and ponder these things in our hearts in imitation of the Blessed Virgin Mary. At the end of the Gospel, the ordained minister kisses the page to show his affection for the sweetness of the words of Christ.
In the homily, the faithful return to the seated position, being receptive the to Word as it is unpacked. The silence after the homily is the perfect time to ponder how one might put these exhortations into one's own life in the coming week.
In the Creed we stand to show that we are declaring our faith, giving witness to God's goodness. We recite the Creed together to show our adherence to our faith in the Lord and our unity in doing so. The Creed is the perfect thing to launch us into the Liturgy of the Eucharist. We have just been nourished with God's Word and had these Mysteries unpacked for us. We claim their as our own in the Creed and then look forward to the Mysteries Incarnate in the Liturgy of the Eucharist.
But first, we remain standing for the Universal Prayer, offering our petitions for the good of the Church, the world, and ourselves. Responding "Lord Hear Our Prayer" in unison make the prayers our own and shows our unity in doing so.