Over where I am, I use scoot:
"Hey, could you scoot over just a bit?"
Or I could be a little more blunt (but it isn't really considered rude) and say: "Could you move over?" or "Could you move, please?"
If you aren't sure, you should probably just try to use the easiest word and say please. Most people can tell if someone doesn't have a complete grasp of the language, and will accommodate them.