Alexander led 35,000 troops intro Asia Minor, where the Persian military made a series of bad decisions that resulted in Alexander readily overtaking all the port along the Aegean Sea coast from Asian Minor to Egypt. In order to accomplish the numerous sieges required for this task, he used Greek technology, which was superior to Persia's.
Tyrants of Greek cities of Asia Minor were expelled and democracies were installed. Alexander continued his conquest of Persia, yet added a unique twist later on by marrying a Persian and forcing his army to take Persian wives as well. Even after pursuing the Persian King Darius relentlessly, Alexander organized an honorable state funeral and then executed the King's murderers.
Alexander had to, from this point on, continue revising his military tactics as he conquered new territory. Upon entering Afghanistan, he befriended one of the region's princes after enacting guirrela warfare. This was a sign of Alexander's ability to seize control of a region while respecting those who inhabited the land prior. While overcoming India, Alexander's army wore out and he had to return to his homeland to appease them. They took many of India's intellectuals to Greece.
Once back in the seat of his empire, Alexander reorganized his empire. He meshed previously incompatible cultures and had grandiose plans for upcoming decades. Unfortunately, though, he died.