Check employment references. Ask questions about the applicant's honesty, integrity and tendency toward violence. Even if past employers refuse to answer the questions, it shows a degree of due diligence. Find out where the applicant has lived during the past ten years and check criminal histories in those states and those counties. The list above are suggestions only.
Laws vary from state to state.
What questions can be asked during an interview and to what extent vary. Consult a lawyer or check with your legal department before implenting changes in your hiring process.