Work part-time, do internships, volunteer, etc., in the field you want to work in while you are in college (and even high school).
30 years ago, back when I was in High school, I got a part time job after school working in an old peoples home. Basically I worked in the kitchens, helping to prepare the evening meal (dinner), setting the tables and doing the dishes after. This particular old peoples home did NOT have any automatic dishwashers. I was paid something like $4 an hour for 3 hours work, 2 days a week and also every second Saturday.
I lasted in this job for 2 years before I was finally asked to leave. And the reason they asked me to leave? Well that was because I would spend too much of my time reading all the books the old people had on their shelves, and not enough time actually doing the job.
I was more than happy to leave when they asked me, since I was quite bored doing that job. Two years is a long time to stay in one job. Well, it is a long time for a teenager anyway. And it was NOT teaching me any skills that I could use in the workforce.
With my love of reading, what I should have done was to volunteer at the local public library. But then again, I probably would spent all my time reading instead of re-shelving those books.
I personally would NOT get any part time job flipping burgers at McDonalds or any other fast food joint - unless you do want to work as a chef or be in the hospitality trade, Then flipping burgers and waiting on tables would be the perfect kind of experience to get.
Not everyone knows what they want to do when they finish High schools.
But if I had been given the choice back when I was in High school, to flip burgers, or write a semi-regular column for a community (free) newspaper, I would have chosen the writing,
You can save the clips and use them for your writing portfolio. You cannot do the same when you're waiting on tables or flipping burgers.
As for internships, I think any business offering unpaid internships, should be required to pay the equivalent to the bus fare on a monthly basis, (perhaps pay for or provide a monthly bus pass?) as the absolute MINIMUM.
After all. the intern is not earning any other money. How do you expect them to travel to and from your office? Cars and buses do cost money. You don't want to be sued for using free labour in a job that usually has a salary tagged to it.
Otherwise, I suggest that students ONLY look for and apply for the PAID internships.