I believe all the above answers are correct, as far as "tradition" goes. A right-handed person holding the knife will see the "obverse" or "presentation" side of the blade towards them, and that's usually where the maker's mark is. (Tip pointing to the left, edge down.) The mark is usually parallel to the guard.
From what I've seen online and in books/magazines, most ABS members put their personal mark on the "obverse" side, and their JS or MS stamp on the "reverse" side.
Now then, do you orient the mark so the guy holding it can read it, or the guy he's showing it to can read it? It seems the latter is more common. Why, I don't know.
As for me, I don't like ricassos in general, although they do look cool on big honkin' bowies and camp knives. I think they're wasted space on most knives that actually get used a lot. I prefer the cutting edge to come as close to the handle or guard as possible on hunters and utility knives, etc. Ever try to peel an apple, strip wire or whittle something with a knife that has a too-big guard or 1-inch ricasso that prevents you getting close to your workpiece? I find it easier to get my thumb in the game and/or have the sharp edge right up close for leverage and fine control.
So,I like horizontal maker's marks on the blade itself, obverse side, oriented close to the guard and spine.