Remember, anyone can buy an envelope machine, but it takes talent to hire the right person. Use industrial psychologists. For hiring key employees, industrial psychologists are valuable tools. But if you have some specific concerns, they can laser in on the problem. If I'm not worried, that's the end of the interview.
Agreements prevent disagreements.
I strongly believe in written contracts. If you are willing to fight your guts out for an agreement, you won't have a disagreement. There is one overriding philosophy that you have to keep in mind for every person you hire. Never compromise your standards. The single greatest mistake a manager can make is to make a bad hire.