Here is what I generally use (I play at a RCC)
For traditional opening and closing hymns:
Great all 8 and 4, along with all the Swell 8s and 4s with box halfway open and Choir 8,4,2 coupled to great. Pedals, regular organ bass 16' with all coupled to pedal.
2nd verse: Add swell reeds, box still halfway open.
3rd verse: remove swell reeds and add 2 and mixture on the great
I tend to use the same registration from the opening hymns and play on the Choir in the verses.
Choir: Clarinet 8'
Great: Diapason 8' with Swell to Great
Swell: Flutes 8' 4' Box closed
Pedal: Organ Bass 16' with Swell to Pedal
In the introduction I use the Clarinet to introduce the melody, accompanied by the swell flutes on the chords and pedal bass. The first time the cantor sings it, I accompany him/her solely with the swell. On the repetition where the congregation is invited to sing, I play on the great and add the great to pedal and open the swell box. For the verses I then play on the swell with the box closed, and on every repetition of the refrain, reopen the box and play on the great.
Offertory and Communion Hymns:
I tend to use mostly flutes for these: The Great 8'4' flutes, or the Choir 8,4,2, or play all on a Great diapason 8.
Same as Gloria
Same as Psalms
Same as Opening Hymns and ending last chord with added Mixture and Trumpet from the great.
Lamb of God:
Same as Offertory Hymns
This is very specific to the organ I am at now. In the past I do different things for different organs, depending on how loud/soft some of the organs are and depending on congregation.