Internships are by far one of the most valuable aspects of any design student’s journey (I did two!). You can approach an internship search in two ways:
1. You can use your internship requirement as an opportunity to dig deeper into a particular sector or specialty that you've enjoyed in your classes and think you might want to pursue. Be sure to highlight the reasons for your interest in the interview and show as much work in this area as you can.
2. If your main concern is hireability after graduation, you can look for an internship that specializes in work that currently has a strong market. Have new, more expansive density regulations been passed in your area? Look at residential. New funds for schools or hospitals? Look at education or healthcare. This is a very analytical approach to your early career, but it is a solid way to start.
When you’re a student, it’s assumed you don’t have professional work experience pre-graduation and your resume will reflect this. Your portfolio should show the work you’ve done in your studio classes, but on your resume you’ll want to call out a couple of specialized classes you have taken at this point in your degree, such as lighting design (have talking points ready about types of calculations you’ve studied), sustainability, ADA/universal design, housing/zoning/urban planning (whatever your school calls this), etc. In summary, go deeper than just your software knowledge to the other aspects of design that have shaped you so far.
In preparation for the internship interviewer asking you to speak about yourself, get very clear on how your unique background influences your abilities for this role. You have transferable skills from so many aspects of your life: your campus job, your volunteering, a personal project, etc - make sure you outline which skills are relevant to yourself and get comfortable speaking about them ahead of time. Also be aware of your strengths and weaknesses compared to your student peers, and practice articulating ways that you have invested in your skills outside of studio class.
Portfolio diversity as a professional means a variety of scopes, sectors, technologies, etc. However, as a student, where a varied career is not assumed, portfolios that demonstrate any real world experience outside of the studio counts toward diversity. (This is where internships come in.) If you have the opportunity to participate on a design project at your internship, wonderful. This translates very easily to your portfolio. If, however, your internship is in some form of design retail, as my own first internship was, you will need to arrange the visuals of your work there in a narrative that articulates the transferable skills you gained there. You can create drawings and renderings to accompany your work to round out the presentation.
Most design professionals have a generous attitude toward students and interns, as we all remember the days when we were in your position. To get the best networking experience during your internship, make it easy for them to help you. Find brief, manageable requests you can make of them, eg: "Could we schedule a time in the next two weeks in which I can ask you some questions about your career?" or "Would it be possible for me to shadow you on X task or meeting next week?". When your requests come well prepared and are easily achievable, you'll have much greater success and you will (deservedly) come across as responsible. And, if you can, think of a task you can help them with in return for their time.
Please make every effort to complete at least one internship before graduation, even if it isn’t a literal graduation requirement. This was the aspect of my own education that I felt best prepared me for the real world of being a designer. All of your classes provide necessary information that you will draw on throughout your career, but it is a different experience entirely to be in a work environment, watching operations and processes and observing professionals with years of practice under their belts. I find it unsurprising that so many programs make internships a requirement, and I hope that in doing so they will provide resources to aid in placement. I wish you the best of luck on your search and hope this has helped you prepare for your interviews and beyond!