One of our biggest lessons was one of the most painful one. We were hiring for a Marketing Director where the client made an offer to the candidate who charmed both our consultants and the client. The Client in his enthusiasm waived reference checks and we jumped a step.
One week in the job, client had suspicions about hired executive not driving company car but having a friend drive the car and asked for reference checks. First call to check references on previous employer using our own grapevine, we learned candidate was fired due to lies, cheating and theft from previous employer.
This lesson was no matter how charming or impressive the candidate seems to be, always check references and always including our own grapevine, not only on references provided by candidate.