Don't be afraid to ask a job candidate "If I hire you, will you stay with us for a reasonable period of time?" Listen to your candidate's answer. Does it show he has grown and developed as a person over the past couple of years? Is he ready to settle down and focus on long-term rather than short-term career objectives? Is he in control of his personal life and does it fit into his career objectives? Remember, you are technically not allowed to ask personal questions during an interview. However, most candidates will divulge quite a lot of personal information anyway. Listen carefully to what they say about their personal lives. Anyone with an unstable personal life probably doesn't have a very stable professional career either.
Excerpted from Attracting & Rewarding Outstanding Employees