In the following photo, you might notice a pattern emerging.
When I was growing up, there were strict rules for decorating our 3D tree. (I'd call it real, but it was artificial. It looked awesome though.)
We used to use colored lights for the bottom two-thirds of the tree and then white lights on top. In the white light area went birds, angels, and the like. Over time the inside would get filled up first with plain balls and then the more special ornaments went up on the outside. Finally, the icicles would go on either as tinsel or the glass ones we first bought in Maryland.
I tend to follow that rule when I do my tree.
I do; Jennifer does not.