In our case, it came down to two D-III schools. One school has open tryouts every year, and returners must try out as well. The only guarantee was the chance to try out.
The other school, and the one that appealed to my son, was up front and the coach point blank told him that when he actively recruits a player, and that player commits with a deposit, he will be on the team--and the rest is up to the player to perform. They do have open tryouts in the fall, but my guess is that is to fill the roster, as needed, when players don't show up as expected.