Check the website of individual schools, since each school have different DAT average. Just get higher than what the school post there and you should be fine (unless your GPA is 3.0 or below).
However, if you want a general competitive DAT score, I would say 20 or above on all categories.
Unless your gpa is 3.2 or lower you don't need 20. When a school's average for the entering class was 17, obviously half the people they took had a DAT of 17 or below.
To reiterate what other people are saying, it depends on the school you're applying to, your GPA, and let me add other factors like who you know, past experience, and how early you are in the cycle.