Doesn't really much matter--anything will work. If you want to make it easy, Whole Foods (and I assume most grocery stores) sells "bread for stuffing" in bags, already cubed. (And they charge too much for it, IMO, but darn it's convenient.)
Just throw it on a baking sheet and toast at 250 for awhile so it's good and dry.
Now that DS is gluten-free, I do it with his gluten-free bread and also I'm making a gluten-free cornbread, to do half-and-half. With Earth Balance instead of butter, it's a GF, DF stuffing.