This is taken from Northcoast Academy's 2012 Battery Percussion program.
Right Hand Grip
Start by holding the right hand palm up, fingers together and thumb
open (creating an “L”). Place the stick across the hand so that 1/3rd of
the way up the stick, the shaft lies on the middle knuckle of the index
finger. Next, the shaft near the blade of the hand should contact the
palm about a ½ inch below the pinky knuckle. From here, curl the
fingers around the stick and follow that by pulling the thumb into the
stick, effectively closing the hand. As you look at your grip, your thumb
should be just slightly to the left of parallel with the shaft of the stick.
The space between the thumb and index should be minimal, if there is
any space at all. The back of the stick should never slide into the crease
in the middle of the palm near the wrist at any time.
Left Hand Grip
Start by holding out the left hand, as if shaking someone else’s left
hand. Place the stick as far back into the pressure point between the
thumb and index finger as it can go; squeeze the thumb toward the
hand, gripping the stick. The stick should be gripped at this point 1/3rd
of the way up the stick. Curl the index finger on top of the stick, and
place the thumb on the index finger. The thumb should contact the
index finger either on the 3rd knuckle or between the middle and 3rd
knuckles. The index finger (from tip to middle knuckle) should be just
about perpendicular to the thumb (The position of the index fingers and
thumbs of both the right and left hands should be nearly identical, with
the exception of the space between the thumb and hand). Next, curl the
middle finger next to the stick in the same manner as the index, with
the tip of the finger sitting on top of the stick (the middle finger should
never be used to produce a stroke). The ring finger should be curled
under the stick and support it from underneath, with the stick sitting
between the 3rd knuckle the cuticle. The pinky curls in next to the ring
finger and is always relaxed. Looking at the grip palm down, there
should be little or no space between each finger.