In my family room, I've used cable staples (like the ones pictured below) to fasten speaker wire along the wall at the top of the baseboards. There are hardwood floors in this room.
Not all of them fastened so securely, which wasn't a problem at first… and then we got a puppy, who bumps into them, and then tries to eat them once they fall out. How can I get them to stay in the wall better, without limiting myself to inserting them over studs (as I sometimes need them more closely spaced than that) or inserting them into the baseboards, which I'd rather not poke so many holes into.