Having written quite a bit of romance lately, it depends on the point of the two characters' romantic relationship are in at the moment. Some I wrote where there's a bit of slow burn going and some mutual pining that eventually ends with a kiss (or further if mutual pining has been going on for sometime). For established relationships, I tend to either have the two characters get used to seeing each other if they're starting or be very affectionate if they've already been together for a while.
With platonic relationships, I tend to have the characters admire and care for one another whether it be friends, family, or both.