I rough dry my hair with my head upside down first, and then I find a thorough blow-dry (i.e. sectioning off the hair and drying it bit by bit) with a fairly big barrel brush helps alot. If you have the time to spare, I also use large velcro rollers on the top half of my head - heat them up with the hair dryer and leave to cool, spray a bit of (volumising) hair spray on them and then carefully take them out.
And then, if you want really really big hair, back-combing at the roots works great. Be sure to leave a small layer of hair unbackcombed on top, to cover the back-combed parts.
And finally, hairspray hairspray hairspray!