Unless you plan on winning Survivor (because that's still a thing) becoming a real life grown up requires a job. And applying for said job most likely depends upon a reference. While the reference may just require jotting down a name and number, it is likely the referral will need to be in the form of a letter. Yes, I'm talking about the mythic letter of recommendation.
One of these references will probably be an academic one, and another required reference will probably be a professional one. Most students assume this professional experience recommendation should come from an internship.
Although this is the perfect opportunity to utilize for a letter, you can also get a recommendation letter from a part-time or summer job, or a volunteer position you held over an extended period of time. So, if you never had an internship, don't panic. Or, if you think your boss from the restaurant you worked at can speak on your behalf better, go for that. After all, it's better to have a good letter that really speaks about you personally than a generic one from an internship supervisor who doesn't really know you.
However, if a professional letter of recommendation from an internship is something you're seeking, there are tricks to procuring it successfully. Take these steps, and, just like Lil Dicky, you can sing, "I'm bout to be professional, Homie, I'm professional."
Take the role seriously.
It may be an internship, but you should treat it like a real full-time job. Even if you're working for a cool start-up or get happy hour drinks with your colleagues, you should always be on your game at work. Arrive on time, work hard during the day, don't abuse your lunch hour (by making it a three-hour break), and get your work done.
Don't just do your work, do it really well. Listen carefully to directions, and ask smart questions and remember the answers. If you are not given regular feedback, ask for it.
Work to implement the feedback you are given, and follow-up to see if your work has improved. This will be a good way to form a relationship with your boss. Also, this shows you are keen on doing work the right way and aren't afraid of criticism, both very mature markers of an individual.
Get to know your colleagues.
It is important to get to know other people in the office, not just other interns. Learn the names of people you interact with or pass in the hall, wish them a good morning/afternoon/evening, and make small talk.
If your superiors take notice, it will show you're a team player. Forming relationships with colleagues might also be a way to get recommended for a special project or full-time position, finding a professional mentor, or creating a nice connection for future professional networking.
Try to get to know your boss personally.
Try your best to meaningfully interact with your superiors. If you have more than one boss (i.e. your boss has a boss) try to get to know as many of these bosses up the ladder as you can. Ease into a personal connection by learning about your boss and their office behavior.
What do they do outside of work? How do they like to work? Acknowledge these interests and preferences and try your best to accommodate them or make a connection through it.
For example, in one of my internships, I printed a report every morning for my boss, stapling the 10 page report together. I started noticing my boss would always eventually remove the staple and paper clip the stack. I then began doing the same, and he very gratefully noticed. It's the little things.
Bosses will get to know people who are personal and on-top of their position. While this is valuable for procuring a letter, it is also a good move to forming a relationship, like a mentor-mentee one.
If you can, do extra work.
If an opportunity presents itself where you can take on more responsibility (and it isn't following a pattern of your time being abused by a boss), go for it. Come in a little early, later, or on weekends, or double down and take on additional tasks during the workday. However, if you cannot feasibly take on extra work, don't worry, this isn't expected.
Ask for a letter before you leave.
Typically, internships will end with an exit interview. If there is not one, schedule one to debrief with your boss on the experience and ask for feedback. This meeting might be an opportunity to talk about a full-time position after graduation. If not, it is a good time to ask for a letter of recommendation.
Ask while you have your boss' attention and they can clearly recall you and your work. It is not advisable to wait until you need the letter to ask, as time may have passed, new interns may have taken your place, and their memory of you may fade.