Chapter 14 tells us that the land to be received by the nine and a half tribes who were to settle west of the Jordan River in Israel proper was determined by lots .
The proposed inheritances were of different sizes. Was it just luck that resulted in Yehudah the largest tribe getting the largest piece of land? Why didn’t the tribes of Joseph get enough land for their people? Why was Shimon’s share so small as to be swallowed up by Judah? It must be the Divine guidance at work.
In his commentary on Parshat V’zos Habracha, Rabbi Menachem Leibtag makes it clear that the location of the tribes’ inheritance was known and that the order of the blessings reflected these geographic locations.
Daat Mikra in Perek 18 gives a possible explanation for how they did the final 7 tribes. They may have done Yehudah first both because he was "first in the fight" and the largest. The 2 and 1/2 tribes already got their land East of the Jordan. They may have done Menashe next in order to finish up the other half of his tribe (Daat Mikra I think), then did Ephraim to finish up Bnei Yosef. Finally, they did the method suggested in Perek 18 for the final 7 tribes, keeping in mind that Shimon was smallest and that he joined forces with Yehudah as suggested in Sefer Shoftim.