Jeet Kune Do changes aspects of different styles to adapt to suit the abilities of the practitioner. Lee felt the dynamic property of Jeet Kun Do enabled the student to adapt to the constant changes of live combat. He believed that only in this situation could a practitioner deem a technique worthy of mastering. Jeet Kun Do requires no memorization of solo forms or "kata". Lee felt that practicing forms without an opponent compared to learning to swim on dry land. He believed that combat was alive and dynamic, changing from millisecond to millisecond.
A Jeet Kun Do student is expected to learn various combat systems and to be effective in all of them. This idea of cross training is similar to the practice of Mixed Martial Arts (MMA) in modern times. Many consider Jeet Kun Do to be the precursor of MMA.
Principles
Three Parts of Jeet Kun DoEfficiency-An attack that reaches it's mark
Directness-Doing what comes naturally in a learned way
Simplicity- Uncomplicated thinking, without ornamentation

Four Ranges of Combat
Kicking
Punching
Trapping
Grappling
Five Ways of Attack
Single Angular/Direct Attack
Hand/Foot Immobilization Attack
Progressive Indirect Attack
Attack by Combinations
Attack by Drawing
Lee incorporated the centerline theory into Jeet Kun Do from Wing Chun. It refers to the imaginary line running down the center of one’s body, the ability to exploit, control and dominate your opponent’s.
Three Guidelines for Centerline
The one who controls the centerline will control the fight.
Protect and maintain your own centerline while you control and exploit your opponent’s.
Control the centerline by occupying it.
For more information about Jeet Kun Do please visit: Jeet Kun Do.

Author's Bio: 

Su Ericksen is a first degree TaeKwonDo black belt and has taught self defense workshops. She lives in the Midwest with her family and works at a large medical center in the cardiology clinic. You may contact her through her website:
Self Defense-4-Women.com.