Almighty and eternal God, in your tender love towards humanity you sent your Son, our Savior Jesus Christ to take on himself our flesh and to suffer death on the cross. Grant that we may follow the example of his patience and humility, and also be made partakers of his resurrection; through your Son, Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and forever.
Source: Book of Common Prayer/Common Worship, after Gelasian, historic collect for Palm Sunday
The prayer above was expanded from a shorter Latin original (Gelasian) that reads:
O God, you sent our Savior to become truly human and suffer death on the cross as an example of humility and patience to be imitated by the human race. Mercifully grant that we may be worthy to have the assurance and the fellowship of his resurrection; through your Son, Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and forever.
Lord God, heavenly Father, in your fatherly grace you did not spare you only Son but gave him up to death on the cross. Pour your Holy Spirit into our hearts that we may find our highest comfort in your grace. Protect us from temptations to sin more, and help us patiently bear whatever hardships may come, so that through him we may have eternal life.
Source: Veit Dietrich, d. 1549, Lent 6 / Palm Sunday
This version of the Palm Sunday Procession with Palms combines elements from several sources. The response: “Blessed is he who comes in the name of the Lord. Hosanna in the highest!” is taken from the Palm Sunday Gospel, and is found in the most ancient Palm Sunday liturgies.
The service begins in the back of the church.
In the name of the Father and of the + Son and of the Holy Spirit. Amen.
Dear friends in Christ, during Lent we have been preparing for the celebration of Christ’s death and resurrection. Today we come together to begin this solemn celebration with the church throughout the world. Christ entered Jerusalem this day in triumph, a triumph that led through suffering and death to resurrection and new life. In faith and love may we follow our Messiah, this humble ruler, who comes riding on a donkey.
Blessed is he who comes in the name of the Lord. Hosanna in the highest!
Let us pray.
O God, to love and cherish you is true righteousness. Increase in our hearts the gifts of your grace. Just as you have given us hope for the things we believe through the death of your only Son, by his resurrection lead us to follow him where he has gone; through your Son, Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and forever. Amen.
A thanksgiving over the palms may be said here:
Let us give thanks to the Lord our God. It is right to give him thanks and praise.
We give you thanks, almighty and eternal God, for sending your only Son in the fullness of time to redeem the world with his obedient life and innocent death. When he entered Jerusalem he was hailed as king by those who spread their garments and palm branches on his path. We carry these branches as signs of the victory he accomplished. Let his victory remain with us, even as we take up our crosses and follow him, that we may die and rise with him, and finally enter his kingdom; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and forever. Amen.
If Palm Sunday is observed as Passion Sunday, the Palm Sunday Gospel is read here.
The Holy Gospel according to St. _____, the _____ chapter.
The Gospel of the Lord. Praise be to you, O Christ.
Let us go forth in peace, in the name of the Lord.
‘All Glory, Laud, and Honor’ or another Palm Sunday hymn is sung. Children, choirs and others may process to the altar carrying palm branches.
1 All glory, laud, and honor To you, Redeemer, King, To whom the lips of children Made sweet hosannas ring. You are the King of Israel And David’s royal Son, Now in the Lord’s name coming, Our King and blessed one.
2 All glory, laud, and honor To you, Redeemer, King, To whom the lips of children Made sweet hosannas ring. The company of angels Is praising you on high, And we with all creation In chorus make reply.
3 All glory, laud, and honor To you, Redeemer, King, To whom the lips of children Made sweet hosannas ring. The people of the Hebrews With palms before you went; Our praise and prayer and anthems Before you we present.
4 All glory, laud, and honor To you, Redeemer, King, To whom the lips of children Made sweet hosannas ring. To you before your passion They sang their hymns of praise; To you, now high exalted, Our melody we raise.
5 All glory, laud, and honor To you, Redeemer, King, To whom the lips of children Made sweet hosannas ring. As you received their praises, Accept the prayers we bring, O Source of ev’ry blessing, Our good and gracious King.
Blessed is he who comes in the name of the Lord. Hosanna in the highest!
The service continues with the Prayer (Collect) of the Day and the Lessons.
Narrative paragraph is modified from public domain sources.
Almighty God,
your dear Son did not ascend to joy
until he first suffered pain,
and did not enter into glory
before he was crucified.
Mercifully grant that we,
walking in the way of the cross,
may find it as the true way
of life and peace;
through Jesus Christ your Son our Lord.
Amen.
O Lord Jesus Christ,
when you entered Jerusalem,
great crowds waved palm branches and cried “Hosanna.”
Save us now from our sins,
and make us to rejoice in you,
our only Redeemer;
through your mercy, O our God,
you are blessed,
and live and govern all things,
now and forever.
Amen.
Scroll through all our Lenten prayers at this link: 
A Collection of Prayers 