Self defense always starts standing up.  So when you are in a situation where your life may be jeopardy, it is helpful to know some techniques to give yourself a ‘fighting’ chance on your own survival.  In this article, we will focus on some basic boxing fundamentals that you can employ in your training.  It is not meant to teach you how to box, but techniques you can learn from boxing.
Jab
The jab is one of the most basic punches in combat sports.  A jab is a quick punch to the face or soft tissue on an opponent or assailant.  It is not meant to be a powerful knockout shot, but is mean to set up for a following punch or kick.  Its use is for element of surprise with its quick explosiveness and lack of telegraphing.  The jab is always used with the lead hand, or the hand in front of you.
Cross
The cross is the power shot.  It is used to knockout your opponent, or at least to deliver some devastating damage to your assailant.  It does not necessarily have the element of surprise as its advantage, but what it lacks in speed is compensated with power.  Because of its execution, it is more telegraphic than the jab.  The cross is used from your back hand, or rear hand.  It is almost always followed up by a jab, but can be utilized with other boxing combinations.
Hook
The hook is used to get around your opponent’s guard, and you are aiming for the chin.  Hitting the chin just right will deliver a knockout blow.  However, in the street, I find it useful when going for areas such as the temple of the head, ear, or other soft areas of the body.  The hook can be used with the lead or rear hands, and can deliver some very powerful shots.  It is also employed with a flurry of other combinations.
Uppercut
Uppercuts also have the ability to get inside a guard, but its sole purpose is to go for the chin.  It has the power and potential to knock out an opponent or assailant by going up underneath the chin.  It is used with either the front or rear hands.  You can use this technique along with other combinations such as the hook, cross, and uppercut.
Conclusion
These four boxing fundamentals are common with most combat sports, and they are very good techniques to start out.  They are used in boxing, obviously, as well as kickboxing and other styles of martial arts.  If you want to know more about boxing, or how to develop these skills, you should seek a reputable boxing coach/gym or other martial arts style schools.