Risa demonstrates one round of Brahma Mudra at a pace quickened for this video. Her eyes lead in bringing her head as far left and right as possible, then back to center. She directs eyes to tip of nose as she brings head backwards, then to a point between her eyebrows as she drops her chin all the way down to her chest. Shoulders remain relaxed and fixed throughout this preparatory exercise. It can feel pleasant to hold the most extreme positions (left, right, up, down) for 2 to 3 seconds each. One minute per round is the correct pace. (A more advanced version would be to keep eyes closed.)
A few rounds of Brahma Mudra can get you in the right state for pranayama, as it has the immediate effect of calming the mind and bringing you inward. It can also be a nice way to cap off an asana class. Just be sure to go really, really slow. It also helps relax the neck and shoulders, bringing about good circulation especially in the regions above the neck.