USE REFERENCES, INCLUDING 'BACKDOOR' WHERE POSSIBLE
Hiring is hard because sometimes candidates are just really good at saying the right things.
One method to counter this is the reference call:
-Asking to speak with someone who has previously worked with and ideally, supervised the candidate.
This helps more accurately learn the truth because it's easy for someone to hide who they are in a 45-minute interview, but much harder (if not, impossible) over 6 months or 2 years in a job.
But keep in mind one thing...
Candidates often choose references who are friends or that owe them favors. Can you blame them?
Unfortunately, this makes it hard to know if references are telling you the truth since they're more loyal to the candidate than you.
To counter this, get 'backdoor' references that the candidate didn't provide where possible.
You'll be surprised how many times this surfaces some crucial insight (be it a red flag or a green one) you find crucial in your ultimate decision.