ian, i also prefer to workout in the morning after i woke up. my warm up consist mostly of stretching and the same as vbm - neck rotations, hip rotations, arm circles, shoulder dislocates and the like.
then, as kevin suggested, immitate what you're about to work out. i normally stand with my feet 2 to 3 feet from the wall and then do "push-ups" against the wall. that gives the muscles that will work during the real push-up a good feel for what's to come.
to warm up for pull-up, i do standing shoulder / military press with a very light barbell - again to get the muscles use to the movement of a pull-up.