I posted this on the bunker about how seeds are determined and what it would take to get Auburn a preferred first weekend site like Nashville or Charlotte. This a pretty good explanation with an example using a recent bracket projection.
This is from AUFamily posted by a poster named ellitor. By far the best explanation and example I’ve found.
Well they use an S curve for the overall tournament. The higher you are on the S curve the higher your chances of not having to travel as far. Only 2 top seeds can play at the same location. Also the conjoining 2nd round match up has to travel & play in the same city as its top 4 seed counterpart.
Here are the 1st round host cities
Pittsburgh
Charlotte
Nashville
Dallas
Whichita
Detriot
San Diego
Boise
Using the top 4 seeds from ESPN's most recent bracket here how the teams match up to the cities:
1 Seeds: Nova (Pittsburgh), UVA (Charlotte), Duke (Charlotte), Purdue (Detroit) Charlotte is full
2 Seeds: UNC (Nashville), Kansas (Whichita), OU (Whichita), Mich St (Detriot) Detroit & Whichita are full
3 Seeds: WVU (Pittsburgh), Whichita (Dallas: Can't play @ home in Whichita), Texas Tech (Dallas), Xavier (Nashville) Nasville, Pittsburgh, Dallas are full
4 Seeds: Zona (San Diego), AU (San Diego), Cincy (Boise), Clemson (Boise) San Diego & Boise are full
There are 4 Regional brackets played in the West but only 1 West team is a top 4 seed so 2 teams from the Southeast & Cincy would have to travel West.