1. Law school will try to rob you of the ability to analyze and recognize systems of power. Lawyers are trained in nothing so well as ignoring the realities of power dynamics in society. "Thinking like a lawyer" mostly involves applying overly formal legal rules while ignoring the fact that they were designed by the powerful for the purpose of maintaining that power.
2. In almost every case, your instincts (about who you are, what you believe, what has real value) are better going into law school than coming out. Find a way to preserve them: through regular self reflection, through conversations with people who know you from before, by writing a long polemic to yourself, whatever method is available to you.
3. The law, as an institution, is fundamentally inhumane, in substance, in practice, and in form. If you’re not careful, law school will make you think that this is the way it has to be.
4. The law serves as a tool for upholding social hierarchy. As a result, law schools try to socialize you to accept hierarchy. It’s in the way lawyers twenty years out ask people where they went to school. It’s in the way law firms care intensely where applicants “rank” in their class. It’s in the way flagship law reviews pick editors.
5. Law school exams only tests for how well you can do law school exams. They do not reflect your ability to practice. Never forget that the people telling you that these exams have value (ie professors) are simply people who were good at taking these exams. Many of them might not even have much experience as practicing lawyers.