The seedings are supposed to snake around, but some of that is affected by conference affiliation.
For example, if everything is assigned purely by seed, the following overall seeds would go to the following regions:
Region A - 1, 8, 9, 16, 17, 24, 25, 32
Region B - 2, 7, 10, 15, 18, 23, 26, 31
Region C - 3, 6, 11, 14, 19, 22, 27, 30
Region D - 4, 5, 12, 13, 20, 21, 28, 29
That's the top 8 seeds in each region by overall seeding breakdown. However, things change when you start working with conference affiliation.
Here's that same list, but with team's assigned by RPI from today's NCAA site (obviously this isn't how the seedings will actually break out, but it gives us something to work with):
Region A - Villanova, Kentucky, Arizona, Minnesota, Virginia, Creighton, West Virginia, Wisconsin
Region B - Kansas, Baylor, Butler, UCLA, St. Mary's, VCU, Xavier, Arkansas
Region C - Louisville, North Carolina, Gonzaga, Cincinnati, SMU, Notre Dame, Maryland, Middle Tennessee St.
Region D - Oregon, Florida, Florida State, Duke, Purdue, Dayton, Oklahoma State, South Carolina
That's all four regions, 1-8. One rule is that conference foes cannot meet prior to the E8. In region C, SMU and Cincinnati would potentially meet in the Round of 32. That means one of them has to move, but you can't create another bad matchup with that move. Wisconsin and Minnesota in Region A would be a potential S16 matchup that shouldn't happen, but because they are lower seeds, they don't get priority.
Additionally, Regions B and C would likely swap 2 seeds to avoid having the top seeds in those two regions both be from the same conference (Big 12 and ACC). Everyone would claim that they put KU and UNC in the same region for the storyline, but the truth is that Louisville and UNC should be split up, and Baylor and KU should be split up, so UNC and Baylor would flip regions in this hypothetical bracket. That same logic would likely move Creighton out of Region A and Xavier out of region B.
So we would likely end up with the following top 8 in each region (overall seed listed):
Region A - Villanova 1, Kentucky 8, Arizona 9, Duke 13, Virginia 17, VCU 23, West Virginia 25, Arkansas 31
Region B - Kansas 2, North Carolina 6, Butler 10, UCLA 15, St. Mary's 18, Creighton 24, Maryland 27, Middle Tennessee St. 30
Region C - Louisville 3, Baylor 7, Gonzaga 11, Cincinnati 14, Purdue 20, Notre Dame 22, Xavier 26, South Carolina 29
Region D - Oregon 4, Florida 5, Florida State 12, Minnesota 16, SMU 19, Dayton 21, Oklahoma State 28, Wisconsin 32
Region A switches it's 4, 6 and 8 seeds, with Duke moving into the 16 spot to separate from Florida State in D.
Region B exchanges it's 2, 6, 7 and 8, but again, it's just a move of one spot up or down.
Region C switches out its 2, 5, 7 and 8, again staying within one spot up or down.
Region D trades it's 4, 5 and 8, and has the largest mover, with Wisconsin (32) replacing the 29 spot and Minnesota (16) trading places with Duke (13).
People would point to Louisville and Cincinnati in the same region, or UNC and KU, or Florida and Florida State as storyline matchups.
Villanova would cry foul that Duke is moved into their region, but you can't leave Duke in D (Florida State) or move them to B (UNC) or C (Louisville), so they have to go to A.
And that's how brackets get made, or made into a mess.