What role did geography play in germanys war plans?

Geography played a huge role. The Schlieffen Plan was designed for just such a war where Germany would face enemies on both the east and west.

The idea behind the strategy was to win a quick victory over France by going through Belgium and taking Paris in a less than a month, which was how long it was calculated Russian troops could mobilize. Germany hoped to knock the French out quickly, as they had done in 1870 but they failed to do so. Additionally, the Germans hope the Austro-Hungarian Empire would take the brunt of the fighting on the Eastern Front but the AH Empire became bogged down in the Balkans and proved to be less than reliable against the Russians.

In terms of naval strategy, Germany's navy did not match the British Royal Navy which denied them access to the Atlantic. Germany hoped to lure out the Royal Navy with raids by battlecruisers and then destroy a significant part of the Royal Navy in a surprise attack. Germany sought to get into the Atlantic in order to open up commerce for herself and to deny it to the British.

Ultimately, Germany knew they were wedged in between hostile powers and planned their whole strategy on trying to knock out opponents in the easiest possible way.