Checking references: "Even if you’ve done all the right things in your recruitment and interview process and you love the candidate and are ready to hire them....

Stop! (Seriously, stop.)

Don’t pull the trigger. No matter how much you may think you've gotten to know someone during the interview process, you can’t know them as well as people who have already worked with the person before. Step back and figure out who you know who has had direct experience working with your prospective hire. References are great, but blind references are gold.  They will prove invaluable, because even if all your instincts turn out correct and she’s a great hire, you’ll gather a wealth of other information in the process -- how best to mentor her, how to get her up to speed faster, and how to complement her in the workplace. And if you turn up troublesome information, you’ll avoid making that costly hiring mistake.  "

How realistic is that?

You can never completely know when you're hiring someone. 

Everyone performs differently in different situations.