Consider the following ideas:
Maintenance of horizontal momentum is the prime key to successful jumping. The athlete who does the best will have the greatest measured horizontal velocity in each of the three (3) phases. Throughout all of your training, try to improve the five points most important to the maintenance of horizontal momentum:
Runway speed. Maximum controlable speed. Uniform acceleration...get faster on each successive step down the runway.
Smooth transition from run to jump. Foot strikes must be in a flat, pawing action. Any toe or forefoot strikes serve to break the action and result in losses in velocity.
Resiliency or Restitution (jump speed). Think "jump forward". Strength work and plyos will help the student of the event to get back in the air from phase to phase.
Rhythm. There is an intrinsic beat or pulse to the triple jump. The feeling is of equal parts. This may not be exactly so, however the cadence sense of the event cannot be denied.
Balance and Alignment. There is a great need to know what direction you are going in the triple jump. If balance is lost forward, backward, or side to side, the result is that the effort will be out of the control of the jumper and in the hands of Sir Issac Newton. Compensation to lost alignment is a major problem in this particular event. It is akin to the loss of control problems that occur in the pole vault accept the jumper is not as far off the planet's surface.
Runway approach must be consistent.
Start procedure: jumper must study and habituate starting procedure during practice.
Stride pattern: rhythm and tempo plus exact number of strides must be reinforced through numerous runway runs during practice.
The double-arm technique has the greatest potential to allow continuity of velocity from phase to phase of the triple jump effort. Athletes must learn to use this technique without slowing down to execute this motion.
At the point of take-off, the double-arm technique is best effected with the use of the arm-and-a-half application. This is measurably superior to a full double-arm at the board and better than the opposing arm technique.