The best way to protect yourself is to avoid a fight altogether, but what happens when you are forced into a fight? You may need to protect yourself through the use of force.
Keep in mind that the ultimate goal is not to beat up your assailant, but to escape from them.
These are 10 great methods for striking your assailant in a way that will disable them long enough for you to escape, with or without a weapon, so that your attempts at self defense will be successful.

1. Stomp on their foot! This particular technique is often available when many of the others are not.
   The downside is that it's not nearly as effective as many of the others, but stomping on their foot can give you the opportunity to use a more effective technique so that you can safely run away.
   
2. Kick their knees! Like most of these techniques, this will hurt! But more than that, it will make it harder for them to chase you when you run away.
   It's generally hard to see this attack coming, making it quite effective.
   
3. Box their ears! By cupping your hand slightly and smacking their ear (or ears), you can cause what is essentially a VERY loud noise VERY close to their ear.
   This can cause intense pain, and can even cause permanent damage if you manage to break their eardrum.
   Either way, intense pain in that particular area will disorient your attacker, giving you ample time to get away.
   
4. Hit their solar plexus! You might have no idea what a solar plexus is, but that's ok, I'm about to explain it.
   It's an area that's just a little bit above the stomach and directly below the rib cage.
   Follow the bottom edges of your rib cage until you get to the highest part.
   There should be a little bone sticking down right there.
   You can either hit that bone or hit just barely below it.
   There is a fairly large collection of nerves there that, when hit directly, can cause intense pain and create the same effect as "knocking the wind out of them", so they will have a hard time breathing.
   If you break that bone, it will be even more painful.
   This will likely stop any attacker in their tracks.
   The downside is that you have a fairly small area to hit, and it's an area that is easily guarded if the attacker sees you going for it.
   
5. Strike their groin! Yes, it's cliché.
   Yes, it's "cheap".
   Yes, it's very effective.
   A punch, a kick, or a weapon of some kind can all work well.
   It can even be effective against females, just not as effective.
   Keep in mind, though, that you may need to use more of an upward motion in your strike if your attacker is female.
   However, it is true that, statistically speaking, more attackers are male than female, so it's relatively unlikely that you'll need to worry about that.
   
6. Hit them in the neck! Necks are very sensitive, especially the front of the neck.
   Striking someone there will cause them to feel like they are being choked for several seconds, along with the pain of being hit in general.
   Keep in mind, though, that if you hit TOO hard, you could crush their trachea and actually kill them.
   This is unlikely, though, because it really takes a lot of force to do that.
   
7. Gouge their eyes! This is one of the most effective methods for disorienting someone.
   By simply jabbing your finger(s) into their eye(s), you will cause a lot of pain, their eyes will tear up, they will be disoriented, and their vision will go blurry for several very valuable seconds, giving you time to run.
   This technique can also cause permanent damage depending on how hard you jab their eyes, how long your fingernails are, and exactly what part of the eye you hit.
   
8. Do a combo! It may sound silly when phrased like that, but doing two or three of these attacks in rapid succession can increase your chance of success and give you more time to escape.
   However, don't let it tempt you to stand there and wail on them.
   It's always better to do only what you need to do and then run.
   

Be careful with these self defense techniques, especially in the way that you practice them.
Many of them can cause permanent damage, and a couple even have the potential to kill somebody, so don't just try them on your friends to see how well they work.
Try them on a non-living target if you feel the need to practice them, but otherwise, save them for an emergency!