Say your story; say it well: Talk about your journey so far, your hopes and dreams—how they transformed you into the person you are today and influenced your desire to be a part of the program you are applying to. Great storytelling allows you to express yourself and detail your experiences and the lessons learned while keeping the reader engaged.
Dip your toes in technical depth: Instead of giving a rough overview of your technical accomplishments, explain them with the consideration they deserve such that the magnitude of the achievement is not lost on the reader. Mention significant technical challenges resolved and use appropriate terminologies for all references to parts of the project. This reflects on your technical capability and your ability to communicate it well.
Goal!: Always mention the end goal you hope to achieve from the internships that aligns with their expectations and future plans on completion of this opportunity. Explain well how you'll utilize the opportunities they provide to achieve them. Give a detailed explanation that focuses on the timeline of the internship and what you'll be doing at each stage as part of it. This shows that you've thoroughly researched the opportunity and are serious about it. It also shows how you won’t require much hand-holding and would be able to utilize everything the opportunity provides systematically (it’s easier to guide a person who already has a well-planned track laid out). If the opportunity has any preferred future goals in store (some programs might be scouting for potential future full-time participants or people focusing on building a career around the particular topic/area the program is focused on) make sure your own goals and future plans mentioned align with them.
Know your opportunity and know yourself: Study about the opportunity (others’ experiences, its mission, expectations, goal, provisions provided, etc) thoroughly before applying. Every SOP must be tailored for the specific opportunity. Talk about what interests you about that opportunity specifically (something unique about them like the opportunities they provide or the projects they're working on) and why it aligns with your own goals and aspirations. It'd be great if you could talk about things you've done or will do as preparation for the role (like reading about the specific area you'd be working on. It’d be easier to work on this part if you manage to get in contact with a potential mentor directly).
Conclusion: Once you go through everything above, you can summarise those points (kinda like reinforcing everything you stated throughout the SOP) to add as a conclusion.