It depends on if it is a paid internship or non-paid. I did both types in college and have had interns here at the shop. I work with the college for their internship program and provide a spot locally for those who live in our area but commute to the college about 95 miles away....
The Intern: Be professional, eager to learn and be prepared to start at the bottom. You will get many tasks unrelated to the job that are just as important as the ones related to the job. You will end up doing the really boring, repetitive tasks others delegate--but get good at them. Be willing to accept tasks that you may think are either below you or that are a bit more than you are prepared for, and do them thoroughly. Do not be afraid to ask questions--it is much better than really messing up due to lack of understanding about the task. Ask for help if you need it--but do not be needy, there are times when you learn by your own thinking process and hands on experience. Do not be afraid to try new things....
As an Employer--I want the person to learn from the ground up. Then they will be equipped to deal with many issues that arise in the every day`business world. I love when the interns offer solutions to problems, take an initiative to streamline and make a task easier or finds a new but more efficient means of dealing with tasks. The intern NEEDS to listen and take constructive criticism in the manner it is meant--not to take it personally but to use it for personal and professional growth. Ask me why, how and what questions!!! I am having them gain experience to teach them the skills they will need in the future--know it all's have no place in an internship. Most important, I need professionalism, willingness to learn and teach each other, and honesty.