A. The invoice you negotiate above is a fake invoice. So don't walk out like you beat the system.
B. This is the best way to negotiate, though. Dealers won't go under their "fake" invoice, it's their limit that most don't know about anyways.
C. Cash is irrelevant these days.
D. Show no emotion, don't express a dire need for the car.
E. Research before you walk in.
F. Have other options from other dealers.