Sorry for the delay. Dog break
Not at the apartment where my hymnal is, so doing this from memory. Intermittent internet [sigh]
Finally gave up and went to get my hymnal [sigh]
In a formal, liturgical, church service, the Pastor leads and the Congregation follows by either responding or joining in, depending on what part of the service it is. The Pastor either faces God (toward the altar and back to the Congregation) or faces the Congregation (back to the altar) depending on what he is doing. If the Pastor is talking to/worshipping God, his back is to the Congregation. If the Pastor is talking to the Congregation, his back is to the altar. The Pastor provides verbal and visual cues for the Congregation to stand up, sit down, come forward to the altar for Holy Communion, etc. The organist provides tones for the Pastor for chants, etc. and audible cues to the Congregation (introductions to hymns, etc.). The liturgy is printed in the hymnal, and the only page flipping is for hymns or something special. Some places print liturgy and hymns in the bulletin, some only print what isn't in the hymnal, some print the litugy but not the hymns. Some places make use of screens instead of hymnals/bulletins, and some use to supplement.
Example patterns of parts of liturgical services (there are many more parts, which use the same patterns as the parts I've listed)
Invocation at the beginning of the service (following the Processional Hymn/Hymn of Invocation):
Pastor faces Congregation and says or chants (sings), "In the Name of The Father, and of The Son, and of The Holy Ghost" and makes the sign of the cross.
The Congregation says or chants (sings), "Amen."
Confession of sins and announcement of grace or absolution (various forms, depends on church or specific liturgy):
Pastor says, "If we say we have no sin, we deceive ourselves, and the truth is not in us."
Congregation says, "But if we confess our sins, God, Who is faithful and just, will forgive our sins, and cleanse us from all unrighteousness.
Pastor pauses for a period of silence to allow individuals to confess silently to God, usually not longer than 30 seconds or a minute (depends on the individual church). Congregations in some churches, and some Pastors, kneel, as able, to confess, which extends the needed time.
Pastor faces away from the Congregation and the Pastor and Congregation say together, "Most merciful God, we confess we are by nature, sinful and unclean. We have sinned against Thee in thought, word, and deed, by what we have done and by what we have left undone. We have not loved Thee with our whole heart; we have not loved our neighbors as ourselves. We justly deserve Thy temporal and eternal punishment. For the sake of Thy Son, Jesus Christ, have mercy on us. Forgive us, renew us, and lead us, so that we may delight in Thy will and walk in Thy ways, to the glory of Thy holy name. Amen.
Pastor faces Congregation and announces grace or pronounces absolution (John 20:23)
Kyrie
The organ plays a short tone and the Congregation and Pastor sing the Kyrie. Since the Kyrie is a prayer directed to God, the Pastor faces the altar and has his back to the Congregation.
Gloria in Excelsis
If the Pastor sings, the organist plays a short tone, then starts playing. The Pastor and organist go for a few bars and then the Congregation joins in (the place is indicated in the hymnal). If the Pastor speaks, the organist waits until it is time for the Congregation to sing to start playing.
The Gospel
Pastor announces The Gospel.
Congregation sings, "Glory be to Thee O God."
Pastor reads or chants (sings) The Gospel (facing the Congregation or in the midst of the Congregation).
Congregation sings, "Praise be to Thee O Christ."
Unless the Procession needs to return to the Chancel, upon conclusion of the Congregational response, the Pastor and Congregation remain standing and start confessing the Apostle's or Nicene Creed. Pastor faces the altar for the creed. If the Pastor and Procession were in the midst of the Congregation, the creed is confessed after they return to the front of the church.
Chants of Psalms
The organ plays a short tone and the Pastor chants (sings) the first line, accompanied by the organ
The Congregation chants (sings) the second line, accompanied by the organ
The Pastor chants (sings) the third line, accompanied by the organ
The Congregation chants (sings) the fourth line, accompanied by the organ
Etc. until the Psalm is finished.
Sometimes, especially at the beginning of Holy Communion, only the first few lines are accompanied by the organ and the Congregation chants (sings) all of the lines, the majority of it a capella (unaccompanied) to allow the organist to receive Holy Communion and return to the organ to play the hymn after the chant is fnished.
Hymns
The organ plays an introduction to hymn (sometimes the last couple of stanzas, but this varies) with slight slowing at the end and the last note(s) slowed and extended so the Pastor, Congregation, and choir know when to start singing (at the next note, which will be the first note of the first stanza).
Since singing of hymns is an act of worship the Pastor stands facing the altar, with his back to Congregation or side wall, front pew, etc., depending on church architecture, and sings when the hymn starts and the Congregation starts/joins in depending on how familiar they are with the hymn. Some Pastors have a mic and some don't. Some Pastors, especially older, might sit while singing hymns. If there's a choir, it's singing assists Pastor and Congregation as well. As
@Kem alluded to, some Pastors have greater or lesser musical ability. Congregations grow in musical ability, too. Singing the hymns and liturgy in parts by the Congregation is a nice Lutheran tradition, although no one gets upset if someone just sings the melody
Everyone just needs to make a joyful noise (not necessarily beautiful)
We can really raise the roof on the old, beloved hymns, which the Congregation knows and loves 
It sounds complicated, but it's really not. In most churches, the order of service is the same, except for (church) seasonal changes, and only the hymns, Psalms, and readings change, and if no Holy Communion, the relevant parts for that are omitted. Since there is so much familiarity, people can pay attention to what is being said or sung, instead of fumbling with hymnals. Some churches stand more than others, and I have never seen anyone get upset with anyone, who sits when everyone else is standing, especially older, pregnant, handicapped, etc.
And sometimes Pastors do rest their voices after they get the Congregation started singing on the hymns, especially if older or sick.
Some places with multiple Pastors will have one Pastor lead the service and the preaching Pastor only preach, especially if multiple services, but not always. Unless there's a Vicar, the Sunday church Pastor does it all week after week.
