Talk to them and give gifts they like to raise the Mood to be full in order to kiss.
1 I celebrate myself, and sing myself, And what I assume you shall assume, For every atom belonging to me as good belongs to you.
I loafe and invite my soul, I lean and loafe at my ease observing a spear of summer grass.
On the day of the wedding, go to the church to talk to the character you would like to end the game with.
If you have raised your Relationship EXP with them to be high enough, they will appear at the church.
This excludes Lewis and Joseph who will always be there on the last day.