There's no denying the efficiency of the German mobilization which is likely what you're referring to. To understand this you have to understand the Schlieffen Plan. The Schlieffen Plan was the plan created out of necessity because of Germany's position in the early 20th century. They were essentially encircled. British blockades to the North, French to the West, and Russians to the East. Their only plan, or rather their best, in the event of war was a quick strike. According to Schlieffen the German army would have to mobilize and strike out France through Belgium within 900-950 hours (~40 days) before the Russians would be mobilized and attacking East Prussia -- the heartland of German and Prussian culture and nobility.
The speedy mobilization that was organized down to the 't' was born out of necessity, basically. They were on such a tight time frame that Schlieffen, who already had quite the eye for detail, planned said mobilization and attacks to the minute. This culminates in 1.6 million soldiers of the west army -- almost 1000 infantry battalions -- rolling across the Rhine River at the rate of 560 trains of 54 cars per day. Another form of the swiftness of the mobilization was the public support. Abysmally small numbers of men dodged conscription. I do not have precise numbers for the Germans in front of me but for the French the number was 1.2% of the 1914 conscripts failed to report for duty. That gives you an idea of what I mean by "abysmally small". It went so well that Chancellor von Bethmann Hollweg was allowed to shelve multiple plans to arrest unpatriotic dissenters, mostly Socialists. The Social Democrat Party, one of the major anti-war parties in Germany, even voted to give large amounts of funds to the mobilization effort.
This is a bit of a loaded question though. It tries to paint that the Germans were inherently superior to the French (who I'll be focusing on particularly) during the onset of the war which is patently false. The Germans fell into the same trap as the French, believing that infantry were the primary fighting force still. Charles Repington of The Times of London in October 1911 said after watching German military maneuvers that *"No other modern army displays such profound contempt for the effect of modern fire."*^[1].
Another glaring area of neglect was modern communications. This is something I really want to emphasize here -- the Germans had nothing short of contempt for electronic communication. During their tenures and even during the war for the latter Schlieffen and Moltke alike were content to deliver orders manually via horseback. On the outset of the war the Germans only had a planned 40 telephone companies but most were still being created so their reserve of 21,000 carrier pigeons were used in their stead. Yes, on a modern battlefield.
Where the German success' come is not in an inherent German advantage but an inherent French disadvantage -- the cult of the offensive as it is commonly called. For example, in December 1913 regulations it said *"The artillery does not prepare attacks, it supports them."*^[2] Less mobile artillery was thrown out for things like the 75mm rapid firing field gun which was used because it could keep up with rapid infantry maneuvers. I do not think I can stress enough about the French's war plan of offensive first before anything else. It was ingrained in their military doctrine and as we'll see later it costs them dearly.
This was born out of General Joffre's vow to never allow the French army to be encircled and destroyed as it was in the Franco-Prussian war just decades earlier which allowed the formation of Germany. "The French Army, returning to its traditions," he wrote in the aforementioned regulations, *"accepts no law in the conduct of operations other than the offensive."*^[3] Few officers appreciated the gravity of the situation that the 120 75mm guns in the French arsenal might get outmached in an all out offensive slugfest against the Germans armed with 108 77mm guns, 36 105mm guns, and 16 150mm guns.
A few days after the declaration of war, the French attacked the city of Bonneau in the Alsace-Lorraine region -- their shared border with Germany. On the 9th of August the counter attack from the Germans commenced. The orderly, shoulder to shoulder advance quickly fell into absolute chaos. Fighting ensued in a heavily wooded vineyard and fighting was close quarters. Heat and exhaustion were primary combatants. Men were dropped off in roadside ditches. Men fought in building to building fighting and many companies fired off over 15,000 rounds blindly and friendly fire among the Germans and French alike was rampant. Night warfare was something very new but something that would become very prevalent in this upcoming war.
The Germans, who were unique in that they used their reserve troops on the front lines, sent their troops in against the French at the Rhone-Rhine Canal. The French unloaded on the Baden Landwehr (reserves/militia, basically) with machine guns. Retreating got so bad that Major Otto Teschner only stemmed the tide by threatening to shoot deserters on sight. From this point on the Germans would also face a familiar foe -- francs-tiereurs. Regular people with hunting rifles firing on the Germans from concealed positions, and it ravaged them. To the point where the Germans were going around burning down villages, executing civilians, and holding priests hostage.
The German early war was one plagued with incompetence. The Southern forces on the shared border with France and Germany near Alsace-Lorraine served one purpose -- defense. They were to hold the French in place while the Hammer swung down through Belgium and surrounded the French. That was their job. Well, Von Moltke the Younger would learn that the strategy of allowing a loose command structure became less plausible on the modern field with hundreds of thousands of men over a multiple hundred kilometer wide front.
General Krafft and Crown Prince Rupprecht, the leaders of the Southern forces, were insistent on taking matters into their own hands. They intentionally retreated onto German territory to goad the French into a pocket and try and encircle them. When it did not work they told the central command, "One either lets me do as I want or one gives me concrete orders" in regards to their request for a direct offensive into French territory. What's even worse is that not only did they do this with their own men, the campaigns in Belgium were going so well Von Moltke even diverted troops down to the Crown Prince to assist his offensive which would only bleed and distort the German plan even more. They would be later explicitly blamed with taking Bavarian noble interests over the interests of the German people as a whole and those accusations would not be far from the truth.
Their attack disintegrated into a mess almost immediately. Although they routed the French back to their defensive fortifications at Nancy, the attack was still a blunder of epic proportions. Low level guerrilla warfare by francs-tieruers dominated German morale. Hills and vineyards and hills and fallen trees became holes for marksmen to pick off hundreds of Germans. Paul Pouradier of the 58th RID infantry brigade describes the chaos: *"The wagons bump each other and collide. Shafts splinter. Horses spook and collapse. Oaths and agitated cries ring out into the arkness. One artillery piece even falls into the stream alongside the road. Suddenly, shots rang out. Now, the disaster is complete. Whoever has a rifle or can lay their hands on one begins to shoot about wildly."*^[4] It took several hours to restore order.
So basically, the Germans weren't any more inherently organized or professional than the French. Sure they were drilled and marched in lockstep but at the end of the day everyone was taken by surprise by the devastation of the First World War. The French charged into artillery with their smaller, maneuverable cannons and cavalry thinking maneuver warfare was still the key and the Germans marched shoulder to shoulder in line formation into French machine guns at Morhang-Saar, Luneville, and the Siege of Liege.
Were they more organized? Well that argument can certainly be made for the mobilization and deployment, in the execution and the combat itself I don't think that would be a fair generalization to make. Unfortunately, for both the Germans and your claim that they were 'more effective', when you plan everything down to the minute when anything goes awry things get thrown into quite the mess right away. Fortunately for the Germans, the French were even more disillusioned about warfare because of men like Joffre and also charged headfirst into artillery and machine guns and completely ignored the idea of a German invasion through Belgium until it was too late.
By the time the Germans had rolled over Belgium and were tearing apart Northern France and Joffre realized that the German attack would not be coming through the center it was too late and the French would be forced to retreat until they reached a collection of rivers that would empty into a larger river named the Marne where they would dig in, fortify, and beat the Germans back and send the war into what we now know as "trench warfare".
tl;dr:
The reasons for German effectiveness in the war was the French insistent on maneuver warfare gave them a significant disadvantage in the artillery department which would come to dominate the war. Joffre's obsession with the cult of the offensive sent the French into unnecessary meatgrinders, weakening them with their already significantly lesser manpower reserves and perhaps most importantly the General Staff's refusal to take any action against the German advance in Belgium until it was far too late.
The German being more 'professional' and organized was born out of the Schlieffen and later Schlieffen-Moltke plan which called for a rapid defeat of the French combined with Schlieffen and Moltke's obsessive attention to detail. Other than that however I do think it's unfair to classify the Germans as somehow inherently more organized, professional, or efficient than the French.
It was the Germans who sent wave after wave of Landewr militia troops against French machine guns. It was the Germans, never the French or Belgians, who responded to defeat by burning entire villages and punishing guerrilla's by slaughtering and deporting thousands of French civilians and committed what is now known as the "Rape of Belgium." (for very good reasons) They were not robots of professionalism. They were human beings just like you and me and they acted on emotion and fear and anger once the bullets started flying.
Notes:
[1] Hew Strachan, The First World War, p.239
[2] Robert Doughty, Pyrrhic Victory: French Strategy and Operations in the Great War p. 27
[3] Ibid p.26
[4] Deuringer, Die Schlact in Lothringen, p. 544
Everything else: Holger Herwig, The Marne, 1914: The Opening of World War I and the Battle that Changed the World and the aforementioned Robert Doughty, The Pyrrhic Victory.
The UK Ground forces were essentially an international police force used to maintain its position in its various empires. The UK at that time spent the vast majority of its time and effort on the Navy, as dominance of the seas was pretty much mandatory due to the size of the Empire.
The UK's main fighting force was the British Expeditionary Force (BEF) which was about 200,000 strong. This was arguably more professional, more organised and more effective that the German Conscript army. There is a famous story of the Germans believing they were up against machine gun fire at the Battle of Mons due to the intensity and accuracy of the British fire, however it was just very well trained men with bolt action .303s.
The problem was the BEF was that it was much smaller than the German force, and nearly wiped out in slowing the German armies advance to Paris.
Its worth remembering that the UK was not accustomed to European land wars. They were more accustomed to watching the French and Prussians kick lumps out of each other and ally with who-ever looked like losing.
Source: Hobsbawm's Age of Extreme's