In order to best survive a zombie attack, you'll need to know your enemy.

Zombies, as you've probably seen in various forms of media, are reanimated dead. They can be brought back numerous ways, but they generally have the same general properties and weaknesses.

Most zombies are in some way decayed and have a taste for human flesh and / or blood.  They will seek out these sources of food and devour them like ravenous animals.  Once a zombie gets a hold of you, it's very difficult to get away.  Because of this, the best way to avoid zombies all together. 

Radiation zombies: These zombies are created from radiation and were common during the 50s and 60s.  This is due to the large amount of nuclear testing that took place in that era.  These zombies are not generally infectious (although they can be), and are usually dead that have risen from the graves.  These zombies typically enjoy brains more than flesh.  Under most circumstances, anyone that dies in a radiation zombie outbreak will become a zombie themself.

Chemical zombies: Chemical zombies are similar to radiation zombies but are created through chemical means.  You will usually find these types of zombies near toxic dump sites.  If the chemical is airborne, it might infect living humans.  Many chemical zombies, however, become so due to chemicals being poured on their grave.  Chemical zombies may or may not be infectious.

Plague zombies: Currently, these are the most common type of zombie.  They are highly infectious and any contact with their blood or saliva will turn a person into a zombie.  Fortunately, this seems to be the only way to become a zombie and someone that dies of natural causes will not become one.  The zombie virus typically has an incubation period of 3-18 hours, depending on viral load and medical intervention.  There is never, ever a cure for the plague, so don't listen to any looping broadcast that says there is.  They're just lying to you.  Remember that this type of zombie is very aggressive and will attack without warning.

No place left in Hell zombies: These are a strange type of zombie that comes about due to overcrowding in Hell.  Typically, in this time of zombie apocalypse, people that die will automatically become zombies because they have nowhere to go.  Oddly enough, this type of zombie is usually infectious and being bitten will cause a person to become a zombie.  Fortunately, these types of zombies are relatively rare.

Regardless of how they're made, zombies can be broken down into two major categories. The first is the traditional slow zombie, followed by the new and improved fast zombie. Fast zombies are exponentially more dangerous than slow zombies and need to be taken very seriously.  If you've been out of the zombie killing game for more than ten years, you'll need a refresher: the name of the game is now "fast zombie."  If you haven't killed one, then you are a no one in the zombie killing community.

Here, I'll break down the differences between the two types of zombie.

Slow zombie: The slow zombie, also known as the retro (or traditional) zombie, is one that moves much more slowly than someone walking at even a brisk pace.  These can only overcome you in large numbers and are relatively easy to escape.  Slow zombies have shown some signs of intelligence and are sometimes able to be trained.  If you find yourself in a slow zombie apocalypse, consider yourself lucky.

Fast zombie: The fast zombie didn't even really exist up until about 10 years ago.  These have almost completely replaced the slow zombies and are much more dangerous.  Most fast zombies will be able to run faster than you and most have unlimited endurance.  They also have a significant amount of strength.  Unlike slow zombies, however, they show no signs of intelligence and can not be tamed.  Never stay in the same room as a fast zombie; they will always be trying to find ways to escape and kill you.

The most important thing you need to know when trying to survive a zombie apocalypse is that you you need to avoid zombies.  Zombies tend to congregate in urban areas, so you'll want to stay out of those unless you absolutely need to go into them.  You should always have a buddy with you when you're traveling, but make sure you don't bring too many people.  Your group should consist of no more than 10 individuals, although 5 or 6 is a more desirable number.

The next most important thing is that head shots are the only way to kill zombies.  You can crush their body all you want, but the zombie will keep coming so long as their brain is still intact.  Many zombies will even survive being decapitated and the head will continue to try to bite if you come close.  The best way to destroy a zombie's brain is through blunt trauma.  If you are attacked by a zombie, strike it hard in the head with a blunt object.  If it doesn't die instantly, then keep hitting it until it stops moving.  Then hit it some more.

Guns are another way to kill zombies, although I prefer to avoid them if possible.  Guns are loud and not as reliable as a good axe, shovel, or tire iron.  Plus, you need to aim and take time to kill a zombie.  Guns are useful if you're killing zombies from a distance, but they're an easy way to die if you try to use them up close.  The only thing a gun is good for is offing yourself if the zombie horde surrounds you.

Slow zombies have become increasingly rare, but they do still exist.  If you happen to encounter one, you'll want to dispatch it as quickly as possible.  A few hard blows to the head should do the trick and will ensure that the zombie doesn't come back for more.  If there are multiple slow zombies, however, you'll want to get away from them.  I don't recommend running because you'll just wear yourself out.  Walk away from the slow zombies at a steady pace.  Only break into a run if they begin to surround you, in which case you'll want to get away as quickly as possible. 

Remember that slow zombies are usually easy to deal with and killing them should be considered a luxury.  Don't get used to hunting slow zombies, however, because the fast zombie is quickly taking their place.  You don't want to fall into a sense of safety and security when there are more dangerous foes waiting in the dark.

Fast zombies are what's "in" right now and should be avoided at all costs.  If you do, however, come into contact with these terrible beasts, then you'll want to isolate them and fight them one on one.  A single fast zombie is comparable to fighting a human, except they will only use their mouths to attack.  This is an advantage and you should be able to beat them fairly easily.  Multiple fast zombies, however, are much more dangerous.  The only sure way to escape a horde of fast zombies is to get into a car and drive off as fast as you can or to seek shelter somewhere.

In a fast zombie apocalypse, you'll want to find somewhere that has plenty of water and food - enough to hold out for several years.  You will not be able to escape a horde of these zombies on foot and attempting to is futile.  You'll have less than a 5% chance of success.