Much of the ability to convert the internship into a full-time position came from leaving a good impression at the end of the summer.
1. Give a final presentation. As a summer employee, you're likely only working on a small team within the whole company. But there are many other permanent employees who see you in the office every day. Most of them don't know what you've been working on. Find some time to give an office-wide presentation of the work you've been doing this summer. If there are other interns in the office, invite the other interns to join you. Reserve a room, send a calendar invite to the whole office, and ask your boss if there is budget to provide lunch or dessert. You will be surprised by the attendance, the curiosity of your colleagues, and their willingness to celebrate your accomplishments.
2. Smoothly transition off all your projects. Is every project you worked on completed? Likely not. In that case, make sure to find a full-time employee on your team who can take over the work from you. Sit down with them and make sure they have all their questions answered. Even for the projects you have completed, document exactly what you did, and give that document to your supervisor. They'll likely reference the document at some point in the future when they have questions. And when they open that document, they'll remember you and the great work you did.
3. Send a proper goodbye email. On your last day, it's best practice to send an email to the people you worked with this summer. Use your judgment to determine if that's to your team, your division, your office, or your whole company. Let them know why you're leaving (e.g., you're going back to school) and how to reach you (offer your personal or school email address). If you want, you can also include a brief recap of the work you did. Thank specific individuals you worked closely with or those who offered you mentorship.
4. Schedule an exit interview with your supervisor. In the last week of your internship, sit down with your supervisor and de-brief the internship. Give him or her a heads-up that you'll want feedback at this meeting. Internships are primarily learning opportunities, and feedback is one of the best ways to learn. Also, be prepared to offer your suggestions for improving the internship program. Your supervisor may want to know if you're interested in coming back next summer, working part-time during the academic year, or joining full-time after graduation. Think in advance about your different responses to what your supervisor might say about a future working relationship. Whether you're excited to have this conversation or dreading it, be prepared.
5. Take time to reflect. Before classes start up again, think about what you learned. What did you like and not like about the internship? What did you learn about the kind of organization you want to work for after school? What did you learn about being a good employee? How does this thinking inform the type of work you want to pursue in your next internship or full-time? Writing down your thoughts and talking to a career counselor at your school are both helpful.
6. Be sure to follow-up. You spent a whole summer with these colleagues -- working side-by-side, eating lunch together, carpooling to company BBQs, etc. You've likely built true friendships with many of them, and they'll want to know how you're doing. Before you leave, connect with all of them on LinkedIn and write down their email addresses. Email them periodically throughout the year to let them know how you're doing at school, ask them how they're doing, and inform them of your plans for future employment. They'll want to be helpful, and you never know who can provide the connection to your dream job.
Good luck with the final days of your summer internships!