I'm very new at this, and have found how to constrain an empty's transforms to an object...but I'm unable to constrain an empty's transforms to a specific vertex of an object (I'm using solidified icospheres and the vertex is essentially the "north pole"...but I plan on having several special locations).
It seems that if I place the empty on the correct vertex, select the empty, and then create a transform constraint I can only pick the sphere as a whole for what I constrain to...not a vertex on the sphere's surface. It won't let me go into edit mode in the middle of picking what I am constraining to, and the vertex itself is not individually available for selection.
When my sphere rotates or translates I want several empties to stay on the surface of various special points on my icosphere, and the plane of the original point of mounting the empty should remain parallel to the tangent of the sphere surface (I'm placing empties with xy plane tangent to the sphere surface).
Perhaps this is better done with parenting (though I'd still need constraints for location, scaling, and rotation) plus constraints? Think of it as marking the location of cities on a globe and knowing which way is up or north.