You're looking for three things, generally, in a person: intelligence, energy, and integrity. And if they don't have the last one, don't even bother with the first two.
Buffett is dead on. Here's why integrity is so important in the people you hire, especially your future managers.
You don't question them for their actions.
Hall of Fame football coach Tony Dungy, in his book Uncommon, said: "Integrity is the choice between what's convenient and what's right." When someone leads with integrity, it makes it hard to question that person. People operating within parameters of truth, honesty, and ethics will listen to their heart and do the right thing, even when nobody is watching. Their actions are open for everyone to see; they don't have to worry about hiding anything from anyone, nor do you have to worry about them hiding anything from you!
Trust is developed seamlessly.
When someone exercises integrity and good judgment, trust is gained, especially with those working and collaborating in close proximity. Colleagues see each other as dependable and accountable for their actions. When trust develops, people feel safe in each other's presence and influence is spread within the tribe.
Integrity commands respect.
A person who walks-the-walk of integrity eventually becomes a role model who commands respect. Why? Because integrity is a hallmark of moral authority and ethical leadership; people desire and long for it in others, especially in leaders. If that's you, your tribe will naturally gravitate to your leadership because they respect the decisions you make on behalf of others and the team.
Assess integrity with this question.
Knowing whether to hire someone or pull the trigger, so to speak, on the interview process, is a matter of asking the right questions. Seasoned job candidates with interviewing experience know exactly what "scripted" answers to give to overcome any objections or get around a weakness or negative quality. To safeguard from hiring bad apples, throw them a curveball when they're expecting a fastball, to catch them off guard. Ask a question like this one:
If we ever got into a bind with a client, would you be willing to tell a little white lie to help us out?
That's what one high-level CEO routinely asks to test out a candidate's integrity. If you are asked that question and say yes, expect a short interview and your parking stub validated early. A no indicates a high degree of integrity and a possible good hire.