Walls and Ceilings - pine board walls

I am installing pine board walls in my house. Should I place them vertical or horizontal and why? Should the boards be lap jointed or is it OK to just butt up against each other.
I would appreciate any suggestions.

Boards used as panelling tend to be installed on the vertical rather than the horizontal. Tongue and groove is preferred.

i think thast vertical vs. horizontal is a matter of personal preference, though i would agree that vertical is most common.

butting them against each other is not the preferred option, because the wood will shrink in the heat & dryness of a house and will open gaps between boards. T&G is preferred, but i believe that lap joints would also work.

another benefit of T&G is that the nailing is done on the toungue and is thus covered by the next board thus creating a nailess finished surface.

Two advantages of placing the boards horizontal versus vertical are: If the wall is narrow, and you want to make it appear larger than it is (kind of like a heavy person wearing a shirt with horizontal stripes), and, it is easy to nail, because every board goes across multiple studs.

Consider Wainscott paneling (tongue and groove double width boards). I put them in my office (vertically), and they look great.