3 things you should do immediately after your internship ends

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As summer internships draw to a close, many interns may be wondering how to capitalize on the new connections they've made.

In fact, millennial workplace expert Lindsey Pollak emphasizes that the real work of leaving a positive impression begins after you leave an internship.

Pollak, author of "Becoming the Boss: New Rules for the Next Generation of Leaders" and "Getting from College to Career: Your Essential Guide to Succeeding in the Real World," tells CNBC Make It that there are three things every intern must do immediately if they want to maintain a meaningful connection with an employer.

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Make a solid plan to keep in touch

While smart interns will spend their last few days getting the contact information of their boss and other managers who made their internship valuable, it's also important for young professionals to show those new connections just how serious they are about keeping in touch.

Pollak suggest that in addition to making LinkedIn connections so that both parties are able to see professional updates from one another, interns should mark their calendars to remind them to check in with certain people once or twice a month.

She also advises interns to also make a plan to keep in touch with their peers — not just senior-level professionals — as "everyone is a part of your network."

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Ask for an update on a project you worked on

Leaving an internship having completed all of the assignments that were given to you will certainly leave a positive impression on a boss, but Pollak says if you really want to stand out, check in to see what the status of that project is after you've left the internship.

"A lot of managers have told me they love when interns have completed a project and after they leave, they check in to see how the project is going to show that they really care not just for the work they did, but also the outcome," says Pollak.

Checking in on a past assignment will also allow you to make a deeper connection with a former employer that goes beyond the standard "thanks for the opportunity" follow-up managers are used to receiving.

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Send a thank you note

While sending a thank you note may seem like common knowledge, this one simple step is something many professionals often forget to do.

In a recent survey, 75 percent of hiring managers and HR professionals said they didn't receive any kind of thank you note from most of the candidates they interviewed, with 30 percent saying no follow-up negatively impacted the next steps for a potential employee.

Interns should get into the habit of promptly sending thank you notes — it's an easy way to show an employer just how much you appreciated an opportunity.

"Even if it wasn't perfect," says Pollak, "you always want to end on a high note."

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