Now that finals are over and temperatures are rising, many college students are taking the next step in their careers by taking the leap into the professional world as summer interns. Internships are an opportunity to find mentors, see the inner workings of companies, and exchange the beer and messenger bag for coffee and a briefcase — or a backpack, in the case of summer interns at tech companies.

Before I took my first full-time job with Goldman Sachs (GS) on Wall Street, I spent several summers working a handful of impactful internships. These included interning at Fox Broadcasting, NBC News, and Bloomberg Business News, where I learned the importance of data and understanding consumer preferences, even in creative industries like TV. I finally made the shift from news to finance, when I interned at the investment banking firms of Bear Stearns and Allen & Company. So what did I gain from these experiences — other than awesome resume fodder? Here are some of my most important takeaways that I hope this year’s crop of summer interns will find useful:

Turn out the lights
I’m not talking about saving energy. There is so much to learn as an intern, so you shouldn’t think of it as a 9–to–5 job. When I was an intern, I was the last one to leave at night, because I spent most of the day learning, and the evenings doing my actual work. Work hard. In fact, be the hardest–working person in the office.

Be a sponge
Learn everything you can. Ask your manager if there are speeches, PowerPoint presentations that you can read, or notes from people’s meetings you can review. Sit in on meetings that aren’t directly relevant to what you’re working on, and absorb as much information as you can. Make an impact and help the people around you be successful. Do your core job — that’s for them, but remember that you are really there to learn — that’s for you.

Make an impression
At many companies, there are a lot more summer internships than entry-level jobs. It’s up to you to make an impression so employers will remember you when it comes time to hire. And don’t worry if you aren’t offered a job right when the internship ends. Keep in mind that many high-growth companies may not be doing their hiring at the end of the summer, but later in the year or early the next year. So maintain your network after you return to school. Keep in touch with your supervisors by emailing articles that pertain to their work. Follow them on Twitter, and retweet them or at them, on occasion. A few months after you’re back at school, remember to schedule a coffee meeting to discuss your interests and learn about job opportunities. Bottom line: Be persistent. A company is much more likely to offer a job to someone it knows and is familiar with their practices.

Be proactive
Managing interns is difficult and managers may not have time to constantly check in with you. Be responsible and take the initiative so you get the most out of your experience. Tell your manager and team that you’re willing to take on different types of projects, which will give you exposure to other departments and broaden your experience and opportunity at the company. To make yourself invaluable, take matters into your own hands. Ask for work. Offer yourself as a resource to your team and support different business groups. This will help you expand your footprint at a company and increases your chances for future job opportunities.

Read all answers to the Leadership Insider question: How can you turn an internship into a full-time job?

College doesn’t prepare students for full-time jobs—internships do by Ryan Smith, CEO and founder of Qualtrics.

How to be a killer intern (and land a job) by Kevin Chou, co-founder and CEO of Kabam.

6 tips to get the most out of your internship by Ryan Harwood, CEO of PureWow.

3 ways to turn your internship into a full-time job by Dan Rosensweig, CEO of Chegg.