How Did World War 1 Start ?

I always heard that a guy named Archie Duke shot an ostrich because he was hungry.  No, I'm only kidding.  Here's how it started:

All of the major players on both sides of the conflict were spoiling for war.  For several years prior to the war, all the yet-to-be combatants were engaged in a large military arms race and build-up.  Also, several economic battles were being waged on the imperialistic front.  (Namely, France and Britian were seeking to dismantle the German economy, removing it from competition.)

France, especially wanted revenge against Germany for the outcome of the Franco-Prussian war.  So fast were the forces of the German states that France was humiliated in defeat by the loss of the much-contested Alsace-Lorraine region that borders both France and Germany.

To this end--revenge, and a chance to prove itself on the battle field--France was very quick to urge Russia to declare war on Austro-Hungary for its handling of the assasination of the Archduke Ferdinand.  This would draw France, Russia's ally, into the conflict.  Germany, an ally of Austro-Hungary, would also be drawn into the war.  France wanted this chance and was eager when the day of Germany's involvement arrived.

Britian, compelled by its alliances with France and Russia, was also drawn into war, quite enthusiastically, I might add.  In those days, there was still a romantic notion of war (as there seems to be with many inexperienced generations), especially a large-scale war.  The mood in the air was very similar to that of the people of the United States at the outbreak of the American Civil War.  War was seen as an exciting adventure.  Forgotten were the lessons of the 1800s in Europe, when war was almost a constant political state.

Strangely enough, the willingness by nations to accept high casualties may not be scaled as one would expect, once the war really got going.  Britian and Russia were the most accepting, followed by France.  The least accepting country was Germany.  (You wouldn't expect that from the "bad guys" now, would you?  It is a false view to look at each side as inherently good or inherently bad in World War One, especially when you look at the manipulations of the French government and the economic war waged by France and Britian.)

This is a very brief explanation, but I hope it helps.

Well then where do i start?
There were many little things that triggered it, but mainly it was just Germany wanting to be like Britain and therefore they had to built better things and mainly it was the rivalry.
All the things mentioned above were all little things leading up to the war, but one thing set the war of immediately. This was the assassination of Franz Ferdinand. He was the heir to the Austro- Hungarian throne. He had made many enemies because it was clear that as soon as he was to take over he would make changes. Big changes. While he was visiting the capital of Bosnia and Herzegovnia, to make an inspection of some troops,  he had arranged to be met at the station beforehand and be taken with his wife, Sophie Chotek von Chotvoka to have lunch. A Serbian terrorist group had decided that he should be assassinated and they decided that his visit was the ideal opportunity. Seven young men, who were trained in bomb throwing and shooting were set up along the cars route and they were ready to kill. The first couple of people failed to hit him and after lunch at the City Hall back in the car, another terrorist named Gavrilo Princip stepped  forward and fired two shots. One killing his pregnant wife and one killed himself.

The killer, Gavrilo Princip was arrested by Serbians and Austro Hungary asked them to move him or deport him back. The Serbians refused to do so and therefore one country after another became involved.

An assassination in Sarajevo (June 28th, 1914) caused a conflict in Europe, which soon spread into a war between Austria-Hungary and Serbia (July 28th 1914). This turned into World War One.

World War 1 started by the assassination of Archduke Franz Ferdinand(who was next in line to the Austrian throne) on the 28th of june 1914 at Sarajevo, capital of Bosnia. Bosnia is part of Austria-Hungary, its people are serb. He was murdered by Gavrilo Princip, 19; Bosnian student; Austria-hater; member of a secret society called the Black Hand.
Gavrilo Princip was 19 years and 11 and a half months old. By law he was 2 weeks too young to be hanged. He was sentenced to prison for 20 years but died of tuberculosis in 1917.
The Austrian government claimed that the Serbian government had planned the murder of Archduke Franz Ferdinand. Serbia hated Austria. Most people in Bosnia were Serbs. When Bosnia became part of the Austro-Hungarian Empire in 1908, many Bosnians wanted to break away and join Serbia. The Austrian government was nervous about Serbia; it was looking for a way to teach Serbia a lesson. Austria used the assassination of Franz Ferdinand as an excuse and sent an ultimatum, which means a list of demands, to Serbia. When Serbia refused to do everything that Austria demanded, Austria declared war on Serbia. This happened on 28 July 1914, exactly one month after the murder.

Because eastern Europe was and always will be unstable and aching for war, one guy shot another guy, his country went to war with the other and a web of alliances drew all the major nations into war together!!