Remember PIE:

P.  Proper position on block
  1. Fold front big toe over edge of block to increase balance/stabilization.
  2. Exude Confidence; Seize start position; place weight on the ball of lead foot; grasp block firmlyarm hold is rigid and straight.
  3. Flatten back (rather than rounded/slumped).
  4. Head is down; chin is towards chest; eyes look at rear foot.
I.  Impulse
  1. Tune in to the starter’s cadence.  Practice reacting to the beep.  Shrug your shoulders, jump, or grab something in front of you to warm up your reflexes.  Visualize your perfect start as you hear the beep. 
  2. As the beep sounds, REACT IMMEDIATELY, and get off the block fast.
  3. Hands should push back against the block, arms are rigid/straight by side for an instant, then they surge forward to assume an extremely tight streamline position, prior to entering the water. 
  4. Leg muscles spring up, out and become tense in the air.
E.  Entry
  1. Stretch arms. Hands should be locked with the strongest arm on the bottom; the first breakout stroke will be pulled with the bottom/strongest arm first.
  2. Head is down between arms and pressing against upper arms.
  3. Squeeze abdominal muscles.
  4. Tighten legs and knees.
  5. Point toes.
  6. Enter the water through "one small hole."

EVERY dive should be a RACE dive. Use your practice time wisely. NEVER allow your body to fall, relax, plunge, lean, flop or drop into the water.
EXPERIMENT during practice:    

*JUMP up and out (more than usual).
*SOAR through the air.
*CLAP hands behind your back as you fly through the air, prior to streamline (drill).
*TIGHTEN knees and legs.
*POINT toes.
*SQUEEZE head between arms in streamline position.