Thanks to Sheri for pointing out several fallacies regarding women fighting men who mean them harm, specifically, that a punch/knee/whatever to the groin will incapacitate the man. She's correct (or her male advisers are): It won't. Hollywood says it works, but in fact it has the opposite effect of enraging the male further. I am a male, and I know. I learned how to fight after being kicked in the crotch in junior high.
I am not a martial arts instructor, but I have taught several women how to defend themselves. I have been a bouncer at large bars for a total of four years. You can't do that without learning something about how men fight. Women: If you're attacked, bite your attacker. It may be distasteful. But men don't expect to be bitten. It works. And honestly, the instep or nose is a weaker point than the groin, unless you're using a blade or broken bottle to attack the femoral artery. In my current capacity I'm an EMT, which actually is very useful for self-defense training. If you know the places where a person can most readily be injured to the point of death (so that you can save them) you know where to attack a person when it is your life at stake.
One argument I've found typical in women I've taught self-defense is that most of them have boasted (to me) that they carry a pocketknife, box-cutter, or something similar. The last woman I gave brief instruction to was carrying a box-cutter with which she planned to stab any attacker. It was wintertime. The blade was 3/4 of an inch long, maybe an inch. Most people's coats are thicker than that, even in Mississippi, during November through February. Not much stabbing to be done in that situation. I told her that if she insisted on carrying that particular blade, she should attack the hands, face, throat, or other bare skin, or her blade would be worthless.
The nose, brow, throat, ears are all good targets because they typically bleed freely. A cut brow or forehead will bleed into the eyes, a broken nose or crushed windpipe can be highly demoralizing, and nothing much hurts worse than a broken eardrum. Learn to attack with an eye toward demoralization, which in many cases will end the fight. If you're going to use a knife, try to fillet (forearm, cheek, whatever) rather than stabbing. An avulsion (open flap of skin and/or muscle) bleeds profusely, is terrifying to the recipient, and needs immediate attention, whereas a stab wound is primarily effective if the organs are penetrated.
Anytime you fight to protect a life -- whether it's your own life or that of a child or another who cannot defend themselves -- you must pay no regard to any preconceived ideas as to what constitutes a fair fight. I firmly believe that the only unfair fight is one which is won by an unjust aggressor. If someone is actively threatening your person, and ultimately your life, then nothing you can do should be considered unfair. Your sole consideration should be to take the threat you have been given, and render it into a non-threat. Use common sense. Don't shoot someone just because he yells at you, and don't knife someone who bumps into you at the grocery store. But if your life or meaningful property is being actively threatened, defend it to the fullest extent you can muster. To do less than this would result in an unfair end to the fight.
And finally, practice. Practice with the tools you carry. If that's a small knife or a gun, practice with it. Become comfortable with what you carry daily. Know how to deploy your tools rapidly and effectively. If all you carry are your car keys, learn how to use them as claws. And if all you have are your hands, feet, and head, practice bringing your body into motion. - J.D.C. in Mississippi