Good internships are treasure troves no matter how old you are. They give you the opportunity to make a new start –figure out where you fit, switch your career path, or just find someone who cares enough to help you make good decisions.

That said, the big internship business comes from college students. Eighty-two percent of graduating seniors will have completed at least one internship, according to Mark Oldman, co-founder of Vault, a media company for career information, and author of Best 109 Internships. “In the United States an internship is no longer an optional benefit but an essential stepping stone for career success.”

The time to start looking for a summer internship is now. Some industries, like finance and journalism, typically have deadlines in the fall. Other industries have spring deadlines. But regardless of deadlines, the earlier you start the better an experience you are likely to have.

Brown University holds meetings in November to get students started on the internship process. “Internships are a really important part of career exploration so you should start as early as possible,” says Barbara Peoples, associate director in the Career Development Center at Brown University.

No matter what your age, an internship can help you to know as much about what you do like as what you don’t like. It’s very hard to tell which sort of job you’ll be happy in, and Daniel Gilbert, professor of psychology at Harvard University, says working summers in a few different industries is a good way figure it out. “Don’t ask people, ‘Does your career make you happy?’ because most people will say yes. Instead, observe people in their work to see if you think they look happy.”

Oldman points out that the benefits of an internship extend way past college. “Increasingly recent college grads and even career changers of all ages are doing internships. They are a great way to ignite career interest. But they are also a low risk way to sample a new industry without committing yourself.”

No matter what age you are, you should follow the same advice for evaluating opportunities. Here is the list of characteristics that make for a good internship, according to Oldman:

Substantive work.
Mentoring opportunities.
Some sort of pay.
Chance for gaining permanent employment.
Good quality of life.

So, how do you get one of these plum internships? For everyone, the best source is, of course, your network. But in most cases, people have not been great at networking before they need an internship.

For college students, the next best resource is the campus career center. A career center measures its success by how many students actually get jobs, so they have a vested interest in making sure you get an internship since that makes you more likely to get a job when you graduate. Besides, one of the most important aspects of succeeding in a career is learning to ask for help, so get started now, when the stakes are not so high.

It might seem that you cannot go wrong in the internship department, but it is not without controversy. Many internships are unpaid – toeing the line of labor laws and sometimes even crossing it. And some internships pay, but not nearly as well as, say, a summer job in construction, or a job corralling ten-year-olds at overnight camp. For people who do not have parental funding or a nest egg of their own, subsidizing an unpaid internship is often out of the question.

But Peoples says that even if you are not doing unpaid labor in the field of your dreams, you can benefit from your summer work. You should “know what you are seeking from a summer experience. Even if you are working at a summer camp, think about goals like becoming a supervisor or working in a different area.” Peoples says that “everyone should have learning goals.” And in fact, the process of crafting goals for personal growth on the job might be the most important internship lesson of them all.