First, remember that we are responsible for whomever we hire. We have accountability. Second, require that all candidates provide a work history with contact information for previous employers. If there are gaps in that work history, find out why. Three personal references are also a common practice, but remain cognizant that personal references are almost always individuals expected to give positive feedback.
Many employers use specific reference forms that can be sent to past employers and references.
The form typically has a statement that may be signed by the interviewee that gives permission for his or her work history to be released. This signature makes it easier to get accurate information. Third, make every effort to speak with the person's immediate supervisor from his or her current or previous workplaces. Sometimes a candidate does not want you to contact that individual. This is a bit of a red flag.