Alternate history

Germany just needs better strategy and diplomacy. Germany should defend in the west and attack in the east. Not attacking in the west means no invasion of Belgium. This delays British involvement since they don't have an immediate reason to go to war. I still think they would enter the war because prominent francophiles like Edward Grey. With a later British entry into the war, Germany gets three big advantages. First, British troops arriving on the Western Front later will mean that Germans can afford to allot less troops to defending the west early in the war, which will have positive ramifications for the war in the east. Second, a British blockade being implemented later in the war, means Germany can import key war materials for a longer period of time. Third, without a rape of Belgium, Germany has a much better reputation in neutral countries, most importantly in the US. The only offensive action that Germany should undertake against France before Russia is defeated, is a limited counteroffensive to take the iron mines of Briey-Longwy and gain better defensive territory in the Vosges.

By attacking in the east, Germany can better support its incompetent ally Austria-Hungary. If the central powers look strong in the east, Italy, Romania, and Greece will have second thoughts about joining the war. A stronger performance in the east earlier on would actually encourage Romania to join the central powers, since they had claims on Russia too. With Russia struggling, they are going to pressure the French for an offensive in the west. But, all France can do is attack the heavily defended German border. They are going to be forced to take massive casualties trying to break through. They can't invade Belgium because Belgium's western border is too small for a breakthrough into the Ruhr and that will kill their reputation in neutral countries. They also can't just defend because to do so, would be political and national suicide; they would be seen as essentially giving up. 

As for better diplomacy, Germany needs to not antagonize the US so much. No Zimmerman Telegram and don't reinstate unrestricted submarine warfare. While there is no way for Germany to stop the US from loaning tons of money to the Entente, it's better than having more troops on the Western Front. 

As for Austria Hungary, they need to figure out that Redl is a spy much sooner. Redl leaked all of their mobilization and war plans, as well as the layout of their fortifications on the Russian border. They only discovered his activities as a spy in 1913. They need to discover this much sooner, preferably before 1910. If they do this, their invasion of Serbia would be better and they would be in a better position to attack Russia without significant German support. 

Also, A cool POD that can contribute to a Central Powers Victory: Admiral Essen attacks some Swedish ships (He tried to do this in OTL), forcing the Swedes to demand an apology and compensation from Russia or face war. Due to Essen's popularity with the navy and the public, Russia is forced to refuse. Thus, Sweden declares war and opens up a another front. I like this POD because it expands the war in a drastic way. This POD would create a Scandinavian Front, which nobody in TTL would be able to see coming since Scandinavia is full of neutral countries. 

How does Germany take Korea from the Japanese? There's also no way Germany is going to get their Asian colonies back without some major concessions. If anything, they'll be focusing on trying to get their African colonies back. As the saying goes, possession is 9/10 of the law. There's no way Japan is retreating back to isolation, all the efforts of modernization will be for nothing if they just abandon all the effort they have put into making themselves into a great power. 

There is no way any major power would allow Germany to puppet France or Russia, especially Britain, that would make Germany completely unopposed in Europe. Secondly, both France and Russia have large hostile populations, meaning any attempt at making them a puppet is going to be impossible.

Germany isn't going to annex Austria unless Austria-Hungary collapses. The German government was made up of a majority of conservative Prussian aristocrats, who didn't like the idea of adding more Catholics to Germany. They would only agree to annex Austria if there was a collapse; that would force their hand through public opinion. The Russians are a defeated nation that Germany sees as a threat; why would they give Russia any territory. Central Power plans for Europe show that Serbia was to only lose territory to Bulgaria. The rest of it would be an Austrian puppet state. The Russian portion of Persia is too big for the Ottomans; they'll only get a small piece of territory in the Caucasus.

Britain never joined because of the atrocities; that's what they pushed in their propaganda to justify entering the war. A significant amount of the British government wanted to go to war against Germany because they feared German domination of Europe. That was British foreign policy for the majority of modern history; don't let a single power dominate Europe or else they will gain naval superiority over you. The naval race between the British and Germans didn't help things either; it made Britain much more friendlier to the Entente. Britain wanted to join the war from the start; Belgium was just a convenient excuse for them to justify it to the public. 

Also I agree with HangryBird, Germany needs better diplomacy, i.e not annoying America

What is the historical society about then? I thought you all did historical lectures or something. 

Historical knowledge is very useful in constructing a plausible alternate history. I figured that you all would have crafted alternate history scenarios before. Alternate history is essentially just thought experiments involving history. 

That's the fun of it. Seeing the huge and fluctuating impacts of small changes.