1. Putting the interest of your junior ahead of yours. If your mentee fails, then you take it as your own failure. You stand up and take the blame.
2. Don't mentor someone just to meet your own "mentoring targets", but because you genuinely want to bring someone up to your level. Your meeitng your target or not is simply a by-product.
3. Be patient. Spend time, teach, guide, show the way sternly as you would do to your own son or younger brother. But if you see your efforts are not bearing quick results, don't lose your patience and give up on him or her. Try again. Maybe you are not doing it the right way.