Here is a quick preview to help you prepare:
Conditioning: Don´t Forget about Conditioning as it is the key in preparation. Athletes are asked to perform at their highest level over a 2-3 hour period.

Warm-Up: Create a routine warm-up that will allow you get your muscles ready to perform in testing drills. Note: too often athletes attempt to test while their muscles are not performing at their peak because their warm-up was not sufficient.

40 Yard Dash: Technique, Technique, Technique...during performance testing athletes are often under tremendous stress and subsequently forget about the important techniques that will allow them to record their best times. By practicing proper technique it will be ingrained in your performance and consequently it will be difficult for you to perform without using the techniques you have been trained to perform.

Vertical Jump: Practice the vertical jump without taking a build up step. Too often athletes prepare for this test with taking a drop step to build momentum and then when it comes time to test athletes are not allowed to use the drop step. Also make certain that your training incorporates plyometrics or some type of vertical explosion.

Pro Agility Shuttle: Technique, Technique, Technique...with the right technique even athletes who may not be as physically talented can outperform the majority of the field.

Football Drills: While preparing for a combine make certain that you set aside time to practice football specific drills as well as one on one competition drills.