As many as you have. But, I would suggest doing and reviewing practice tests for this week and using the last week to review all material you still may not be sure about. It is best to not do a practice test the week before your exam because you won't have enough time to let the info learned from it settle/time to learn from your mistakes...especially if you take tests just a few days before. That tends to stress people out because they worry about the score they got. If you spend the last week doing lots of reviewing, whatever practice test scores you got the week before are bound to be higher on the real DAT. 😀