It doesn’t matter if you are an account assistant or a president, we all report to someone. The smarter those people are, the more you will learn. So the trick is to find wise people who you can learn from.
Hopefully, you can find these people when you are interviewing, generally not your immediate supervisor (mostly not senior enough to be a true mentor), but someone who is in your chain of command. And, if not, once you take a job you can identify people who will take an interest in your career.
To find and identify these people may require some work. The first thing you need to do is identify them. To help, I am going to give you my favorite saying (an Arabic Proverb):
He Who Knows
He who knows not and knows not that he knows not,
Is a fool, shun him.
He who knows not and knows that he knows not,
Is simple, teach him.
He who knows and knows not that he knows,
Is asleep, awaken him.
He who knows and knows that he knows,
Is wise, follow him.
By this definition, we all know many fools. So how do we identify the people we want to work for?
First, ask tough, direct questions while you are interviewing. There is no reason you can’t turn the interview around and interview the interviewer. You must be able to engage them in a real conversation so you can ask them how they got to where they are. Their answers and their attitude will help you determine if, in fact, they can become a mentor. Ask them what they think of the business. Ask them what they would change if they were the president of their company. Ask what they are proud of accomplishing in business. Finally, ask how they would teach you or how you can learn from them. You want to determine that you are more than just a body to fill a role. (If you are afraid to ask these questions, there is probably a lack of chemistry and they will just be your boss, not your mentor).
If the company is right, but your supervisor is not going to be your mentor, you must get exposure to others in the company who will take an interest in your career. Sometimes it is your bosses boss. Often it is someone else in the company. If you can, identify those people and then find ways of contacting and connecting with them, so that they can know who you are and what you are capable of. You can always simply introduce yourself.
It is essential to your career that you have a mentor who believes in you. I had one who constantly volunteered me for tough assignments he knew I could do. It got me management exposure and it helped make me a senior vice president when I was in my late twenties.