I worked as a volunteer for about a year before they even considered giving me a full time position. There was no formal interview, rather I was considered for a paid position after volunteering.

I was taking a class from this particular professor. She expressed at the end of a lecture that she was looking for an Undergraduate Research Assistant and that if we were interested to come visit her during office hours. I went to see her and she asked me what I wanted to do in the future and why I wanted to be her Undergraduate Research Assistant. She told me she wanted to talk to a few other students. After a few days she let me know that I could have the job if I wanted it.