To apply siding to the dollhouse, you need to ensure that the side porch trim is dry so that the siding sits flush against it. I realized this too late, after starting the bottom three rows of siding, which left a gap between the porch piece and the siding. I'm hoping this gap will be less noticeable once I paint the siding, as I painted the wall before adding the siding.
I used a basswood strip to set my lap width guidelines, and it seems to be the right size. The lap width for siding is a matter of personal preference; some people prefer thinner widths while others like them wider.
I extended the siding up to where the gable begins, then stopped and added a white trim to create a separation between the two areas.