1. For hair as straight and smooth as Beyoncé's, Julianne's, or Courteney's, start by rubbing a handful of mousse into your scalp after shampooing. Then, spritz sections of wet hair — first at the root and then all over — with a volumizing spray.
2. Set your hair dryer on high and put on the nozzle attachment, which directs heat to the exact area you're working on. Use your hands instead of a brush as you blowdry, alternately going with the way hair grows and against it to maximize volume. Keep going until hair is mostly dry, but not completely — about three-quarters of the way.
3. Now, use clips to divide hair first into top and bottom layers, then into individual sections about two inches wide.
4. Starting with the bottom layer, unclip one section of hair and wrap it securely around the barrel of a round brush. Aim your dryer up, against the grain of the hair, making sure the roots are totally dry before moving on to the ends. Rotate the brush underneath the ends as you dry — this will leave them looking smooth, not brittle. The more you pull with your brush as you dry, the longer your blowout will last. Repeat with each section of hair until all clips have been removed.
5. Finally, run a bit of shine serum through your strands and mist with hairspray to control flyaways.