The fundamentals of a bowling release are the wrist position and the finger release.
Finger release A finger release is how your fingers come out of the bowling ball as you release. A proper finger release is when your thumb comes out of the ball first, and then your middle and ring finger should release last. When the last two fingers come out is what generates the rotation and revolution of the ball. Those two fingers position the ball and by flipping upward generates the speed and the spin of the ball. The most spin will be generated if the thumb is out of the ball by your thigh and then your other fingers. also, to generate spin, your pointer finger should be pointing straight down to the floor because it will position your hand at ten o'clock for a proper and beautiful release.
Wrist position Wrist position is where your wrist is positioned, relative to the ball at the time you let go. Your wrist position may depend on what type of bowler you are, and the conditions that day. There are three different wrist positions: relaxed, firm, and strong. The term relaxed is used for a broken wrist. This is what bowlers' wrists want to do naturally. Usually this form of wrist position is used for drier patterns, because the ball will break later in the lane than a firm or strong wrist will. The firm wrist position is what bowlers use to reference a straight. This position is the normal position for most bowlers, and what a bowling coach teaches you if you are just learning. Finally, the strong wrist refers to a cupped, or bent wrist. This wrist position gives you the most revolutions, how many time the ball will complete one rotation in a minute, out of any position.