You've worked hard for the last three months, take your hard work with you! Be sure to take a few extra minutes to think back and create a list of all of the tasks you've completed over the course of the internship. What will you write on your resume? What results came from your projects? Send or save any of your personal files from the office computer to a flash-drive, so that you can keep it for your records.
2. Request an exit interview.
Getting feedback from your supervisor is the best way to end an internship. You have been learning this whole time, but an exit interview will really sum up your progress thus far. Take all criticism - positive and negative - and apply it for self-development!
3. Give much thanks.
Be grateful for this opportunity! Reach out to any staff you worked with or enjoyed talking to. It's important to let your supervisor know that you were glad to have been a part of the team, even for a short amount of time. If you found anything your supervisor did beneficial, tell them! This may encourage him or her to aid future interns in the same way, and improve the internship program.
How do you feel? Was it beneficial? Did you learn anything? Chances are, you surely learned something, and even if you thought you didn't enjoy the program this whole time, you can most likely take something away from the office environment. Interning allows you to test out what industries, positions, and office atmosphere is best for you - consider that once you complete the program.