From my experience, the best advisors help in three ways: encourage you to look at the problem or opportunity from multiple angles; help you balance the tug of the short-term with important long-term priorities; and ask the tough questions you need to know to reach the best solution.
As you become more senior in your career, it can be thin at the top - It's harder and harder to get unbiased and direct feedback when making decisions. You want people who will speak truth to power. Say no to any 'yes men or women' on your personal board. When you face a personal crossroads, you need honest advisors.
