Modelling character alongside armature

If I want to avoid the problems I came across before I could try to model a character to work with the mocap armature. I started with a cube, and just extruded, this of course is a very simple version but takes shape when I set smooth and add in subsurf modifier.

I tested what would happen if I weight painted, so I added the armature modifier and chose one of the arm bones and weight painted, as you can see it jumped up away from the armature, moving towards an invisible point again... I weight painted the head as well to see if it made a difference. It didn't appear to...

Looking at the tutorial I had forgotten to move the armature modifier up (but below the mirror as it affected the middle - because it wasn't finished), I then weight painted with clicks, as opposed to dragging the brush, and it seemed to work more systematically, getting all vertices.



Once again the problems occurred when the mesh started moving, with various points flying about the screen. It seems the only way I'll be able to use my own character and armature will be to make it follow the empties