Be pleasant and polite to every person you meet when you go into an interview. If you interact with the receptionist in a nice way, they often will mention how nice you were to your interviewer the next time they walk by. Besides, you never know when the person you think is just the secretary is actually the head of the department covering for the secretary who needed to go pick up their kid who got sick in school. This seems like an obvious way to behave, but we've had interviewees who were rude to the security guard who showed them in, or to the receptionist, and it certainly was a mark against them when compared to other candidates who not. My boss has told me that students have dismissed our entry-level jobs at career fairs because either they believe that they want to be doing curatorial or preservation work but misunderstand what that entails, or they want to skip rungs on the ladder and start out by developing new programs.
Internships are a great way to find out who does what and at what level.
Don't dismiss any job as beneath you if it gets you into the right institution, introduces you to the right people, or will give you experience in the right field. In the non-profit field, there is usually not enough money to hire support staff. For example, most people who want to work in museums think they want to work in curatorial departments. Some find out this is truly the area they want to work in, but most people don't realize what curators actually do, and often discover that it's not at all what they wanted to be doing. A job in a department like education,for example, allows a person to interact with many different departments and see which ones they're really interested in, as well as allowing them to make connections helping them move more easily into another department.