Found this
For the initial regional rounds of the tournament, the higher seeded team is always the home team. Once the initial regional round is completed, the NCAA uses the following three step process:
Step 1) The team has been the home team fewer times during the tournament becomes the home team.
Step 2) If both teams were the home team the same number of times, count the number of times each team was the visiting team during the tournament. The team that was the visiting team more often during the tournament becomes the home team.
Step 3) If both teams were the home team and visiting team the same number of times and the teams met previously during the tournament, the visitor in the immediately preceding game between the two teams becomes the home team.
Step 4) If both teams were the home team and visiting team the same number of times and the teams did not previously meet during the tournament, the team that was the visitor in its most recent, preceding game becomes the home team.
Step 5) If both teams were the home team and visiting team the same number of times, the teams did not previously meet during the tournament, and both teams were the visitor (or home team) in their most recent, preceding game, then the home team is decided by a coin flip.