The list that follows discusses characteristics to help identify mentors in your career. Chances are that certain people, whether you have identified them or not, are providing you with mentoring.
A mentor should be accessible.
For someone to provide you with guidance in your career or life, he needs to be available to you. This does not necessarily mean in the form of face-to-face meetings. However, phone calls, e-mails, or requests to meet should not go ignored for extensive periods of time. If you are never able to receive input from an individual, that person is a poor choice as a mentor.
A mentor does not need to be a senior in your chosen career path.
Wisdom and honesty are the primary commodities that a mentor provides. I am not talking about instruction on the latest programming technique or how to configure the latest Cisco firewall product. My mentors have taken the form of managers, a building contractor, a manufacturing executive, and so on. In fact, only one person that I consider a mentor is a technology professional.
A mentor should, at times, make you uncomfortable.
Someone who approves of every choice you make, without question or analysis, is not going to be a very good mentor. Those who play the role of mentor in your career should, at times, play devil's advocate in conversations about careers and profession. They should provide alternative points of view and make you question your decisions. I don't mean in a way that undermines your confidence and makes you fearful of presenting the mentor your ideas, but ensuring that you have taken reasonable steps to see the broad impact of your decisions.
A mentor makes you uncomfortable not because of his attitude, but because he demands good, solid judgment.
You can have multiple mentors.
A mentor is simply someone who you regularly go to for advice. When you are stuck or unsure of your next step, whose input do you seek? You likely consult several people. These people are, whether identified formally or not, serving as mentors.
In fact, I would advocate having several such people for weighty decisions. There is no rule stating that you must seek and take the advice of only one. You might find that three different individuals, all of whom you respect, provide three different perspectives. You might even receive conflicting advice.
This is okay and should be expected. A mentor is not there to make decisions for you, but to provide you with insight into a situation.
Mentors help you see subtleties in situations that you might have overlooked. Remember, however, in the final analysis, the decisions you make are your own.
You might never have personal contact with a mentor.
I broaden the definition of mentor to include those you have never met. For example, significant authors and publications can fall into a career mentor role. They are part of the network of advice you should seek when you are faced with difficult decisions.