Fighting is generally not a good thing and should be avoided. However, sometimes you may find yourself in a situation where you must defend yourself against an assailant.
One of the most important components of fighting is your stance. If you are right-handed you should make your body perpendicular to your opponent, that is with your right side directly facing the opponent and your chest pointing in a direction ninety degrees away from your opponent. This minimizes the area of your body that can be struck and greatly enhances your stability since it isn't as easy to fall.
Your feet should be placed shoulder-width apart and your knees should be slightly bent and never locked. This allows you to move more quickly and be more responsive to any pushing or striking. Your weight should be evenly distributed between the balls of both of your feet, allowing a quick reactive movement. Both of your feet should remain on the ground before executing any punch or kick to help precision. If you have to make any steps, barely raise your feet off of the ground so that you can quickly reconnect with the ground if the opponent makes a move.
Like your chest and torso, the hips should be perpendicular to your opponent. Shoulders should be kept directly over the hips and the back straight. Always keep your shoulders and head back and try not to lean into a punch since it leaves your head open to a responsive punch. It is extremely important to keep your weight centered to make it harder for your opponent to knock you over.
Keep your head facing your adversary with your right fist just under eye level. By keeping the arm directly in front of your body, you effectively block any strikes. The other arm should be placed up around the side of your body with the fist by the chin. This helps protect your chest and abdomen from any rounded punches.
Effective strike points include the nose, ears, abdomen, knees, and the genitalia. If you are facing a male opponent, the genitalia is obviously the most sensitive and unguarded part and a well placed strike can send them to the ground. A kick square to the knee can dislocate the knee or even break it, greatly reducing your opponent's ability to fight. If you punch the head, try to avoid the cheekbones and the mouth, since the teeth can cause considerable damage to your hand.
If your opponent has long hair, do not hesitate to grab it if you are given the opportunity. A grapple on their hair typically causes their arms to flail up, making the rest of their body vulnerable. This strategy also works well with the eyes, in which case a jab can cause the arms shooting up and leave the body open.
If you have a knife you have an obvious advantage and quick jabs to the abdomen can make short work of an opponent. If the adversary has a knife, try to use your feet to knock it out with a quick kick. The rubber soles of your shoes provide excellent protection against the sharp blade and can easily knock it out of their hand.
If you have a gun and they have a weapon, go ahead and shoot, but try for a non-fatal shot. If only you have a gun, go for the leg. If only they have a gun and are holding it, your best chance is probably to try to knock their arm to the side or upwards and take advantage of their occupied arm to attack their open body.
If you get them on the ground, do what you have to do to make sure they stay down. Kick them in the stomach or the head and go for the knees to cripple their ability to get up and come after you later.
Practice in the art of fighting helps a great deal, as does strength and endurance training. Sparring with a friend using boxing gloves or foam pads will help you predict movements and discover weak areas in your defense. Once again, try to use diplomacy or fleeing to avoid a fight, but unfortunately a fight isn't always avoidable.