Since it's the holiday of Hungarian statehood and Saint Stephen, whom this statehood originates from (well, traditionally), we could take a look at his work, at least partially.
The first work he did was done by the sword. (I say first but much of the works was done in parallel.)
It seems to me that when our Ancestors conquered the Carpathian basin, the kagans who lead the conquest and organized the settlement of the Magyars, Álmos and his son Árpád enjoyed great, centralized power. In the times of their subsequent heirs the power decentralized and the power various tribal leaders (often from the Árpád family or relative of theirs via marriages) grew. This could be measured chiefly from two facts: 1. they could lead their own campaigns against foreign lands; 2. they were able to set aside one kagan and elect a new one in his place. Hundred years after the conquest at the time of Stephen the Hungarian lands give the impression to me of a loose federation, where the kagan or Grand Prince was a desired title but had no real power over the chieftains.
Stephen had to fight with their relatives to the title, and then went on and made all the others bend the knee. I think one underrated and often forgotten reason why he had to show who's the boss is the religious differences. And I not mean that the other guys were pagan (which often mentioned in fact overstated), but because due to the relatively independent foreign politics chieftains could pursue, those with ties to Byzantium, the Bulgars, and Kiev often showed orthodogs influences while Stephen himself was oriented to Rome (and to HRE). I see one huge deficiency of Hungarian historiography is the effects of the Schism - and the long road that lead to that - onto the Hungarian politics.
Anyway the organization of statehood was started with the centralization of Hungarian lands. He was so successful in this, that for a long time the Árpáds held such amount lands in their own country, that all the other lords' holdings were dwarfed by it - this has no analogy in Europe.