Pure Silver: A werewolf legend purest will always say that a pure silver weapon (dagger, bullet, spear, etc) is the best way to destroy a werewolf.

Alchemists and sorcerers throughout the ages have used silver for its magical properties. Some interesting points of pure silver is that is has the highest thermal conductivity - the intensive property of a material which relates its ability to conduct heat. Mirrors are made with silver with a process called silvering. Silver and werewolves also have a common connection - the full moon.

The Greeks, Romans, Sumerians, Babylonians, Egyptians, Aztecs, Norse, Native American and just about every other ancient society used silver to build artifacts, coins, talismans, and jewelry ascribed with different powers and significance. 

Silver/Mercury: Now here is where it gets a little tricky. The werewolf legends all say that silver will kill a werewolf. The problem with this is that when these legends were written the metal mercury was thought of as a kind of silver. It was called quicksilver. Mercury can form an ally with silver but it is completely unrelated to silver. Mercury is a relatively poor conductor of heat but is a good conductor of electricity and it can also be used in silvering mirrors.

Alchemists often thought of mercury as the first matter from which all metals were formed. It turns out that there could be a mistake in the translation that silver will kill werewolves. It is very possible that the actual metal used to defeat the were-beast was actually mercury. Better carry silver and mercury bullets just to be safe!

Destroying the Heart of the Brain: Piecing the heart, much like in the case of a vampire, is said to kill a werewolf. Of course, it isn't enough to just stop the heart from beating because werewolves have great regeneration abilities so the heart must be cut out and destroyed, preferably burned.

The same goes for the brain. Any type of skull smashing blow should stop a werewolf just like any other creature. Then, the head must be removed and destroyed to finish the job.  Wolfsbane, with the head severed, and stuffed into the muzzle/snout, will prevent the regeneration of the wolf from transpiring of the ancient gypsyies. 

There really isn't much else that can be done to destroy a werewolf short of blowing them up or dropping them into a giant meat grinder. Werewolves are giant brutes with great regenerative powers. Werewolves and vampires are not immortals. They have weaknesses and they die like every other creature on the planet. Silver/Mercury and destroying the heart and brain are just a werewolf's main points of weakness. Be creative, think outside of the box…I'm sure that is you tricked a werewolf into eating some type of explosive that would probably kill it too.