The importance of a movement assessment:

The body is a chain; each link effecting the others. When one of those links is dysfunctional, the entire kinetic chain becomes weak. Muscle balance is essential to transfer force, accelerate, decelerate, and stabilize. Muscular imbalances can occur from trauma, repetitive movement, stress, sedentary lifestyle, disease…you get the idea. The result will be a functional movement impairment and eventually injury.
Take control of your own well being. First (of course) I recommend finding a qualified trainer experienced in doing movement assessments (call me if you need a referral). If this can’t be done, do a spot check on your self.
The easiest way is to do an over head squat assessment in a mirror.

Stand with your feet hip width apart, feet facing forward. Raise your arms above your head and straighten them at about a 45-60 degree angle to the sides. Slowly complete a number of squats without changing your position.

What you are looking for is:
Do your feet turn in or out, or do they stay forward?
Do your heels come up off the ground?
Do you loose your balance?
Do your knees move in or out, or do they stay forward.
Does you low back round or arch?
Do you have to lean forward to stay balanced?
Do your arms fall forward?

If you answered yes to any of these questions, you have an imbalance that will sooner or later cause an injury to muscle tissue or a joint.

What is trapping and how is it applied?

If there was a way to immobilize your opponents offensive weapons so you could attack with impunity, would you want o learn it? That’s what trapping allows you to do. The trapping range of JKD is a critical element that is left out of most training programs. In a world where schools are teaching Brazilian Jujitsu and Muay Thai Kick Boxing, the art of trapping has faded away. However, trapping is not just a bunch of techniques; it is a range of combat that is largely ignored. We use elements and training methods from a number of different systems including Thai Boxing, Kali, and Wing Chung to develop our attributes in trapping range.

Trapping is a range of fighting. It is the same as clinch range, but without necessarily going into a clinch. Just like boxing has a jab and a cross, and tae kwon do has a roundhouse kick, trapping has a number of techniques such as pak soa and jut soa, as well as head-butts, knees, and elbows. The thought behind trapping is not to grab your opponent as in a grappling art, but to jamb their hands or legs so they can not execute a punch or a kick. The idea is to momentarily disable one or more of your opponent’s weapons so you can effectively execute a kick, punch, knee, or an elbow without the threat of your opponent’s weapons.

Keep in mind that just like a good kicker can execute a kick from kicking, punching, or trapping range, and a good boxer can punch in punching range or clinch range, many trapping techniques can be executed in a the various ranges, not just trapping range.

The use of deadly force

To the unprepared, the shock of sudden and unprovoked violence has a tendency to paralyze the victim with fear or cause doubt in their mind that violence is being committed against them. They are often unable to react or wish it was not happening. Understand that you fight to stop, not to kill. However, you may end up killing or maiming. If you have not made peace, in advance, with that decision, you may not be able to make that decision when you need to. Should you ever find yourself in a lethal confrontation; the decision to use deadly force is going to be yours and yours alone.
This why you must decide ahead of time how much force you are willing to use to defend yourself, your loved ones, or another innocent.
You are universally justified in the use of deadly force when there is a reasonable fear of immediate or otherwise unavoidable danger of death or serious bodily injury to the innocent. All of these factors must be present to justify the use of deadly force. If one of them is missing, you will most certainly face civil and maybe even criminal charges.
You or the person you are defending must be free from fault. In other words, you can not start a fight then claim self defense.
You know when you are in immediate and unavoidable danger when your assailant has the ability to cause harm, has the opportunity to inflict harm, and is intent, as shown by actions or words, on killing, crippling, or permanently disfiguring you.
Lethal force is justified when there is a disparity of force such as:
A large man against a small man
Able bodied against disabled
Man against woman
Two or more on one
Someone trained in martial arts against an untrained person
When do you retreat?
In order to justify the use of deadly force, you must show that there was not an alternative. In some jurisdictions, retreat is required. If you do not retreat until you could retreat no further, then you are not justified in the use of deadly force. In the universally accepted use of deadly force, retreat is always a good idea and should be done if it is a viable alternative and does not place you or those around you in greater danger. Retreat will establish that you did everything possible to avoid the confrontation.
Always keep in mind: if it’s not worth dying for it is not worth fighting for. If you must think about fighting, you probably should not
Paraphrased from an article by Frontsite Firearms Training