You develop a relationship with a person who has more experience than you do, and over time, that person may become a mentor to you. And I say may, because if the person you're working with determines that you don't provide any value to the relationship, they won't be that willing to help you for long.
I say this from experience - lots of people want me to mentor them, and I've had quite a few that, once they got their first job, they just disappeared.
I'm a lot more picky about which college students I mentor now.