SOI was the most challenging part for me, since the word count is so low. My advice would be to start early enough that you can get feedback from people (supervisors, mentors) and redraft redraft redraft until it feels right. Don't be afraid to talk about yourself and what makes you unique! The statement I ended with was much different than my first draft. Look at the mission/values of the programs and try to incorporate that into your letter.
It really helps if you have a relationship with a prof/research supervisor who can work through it with you. If you're in second year, I'd recommend trying to grow those kinds of connections now. It makes a big difference come application time if you have referees who know you well and are willing to support you throughout the application process. I felt confident about my referral letters + was even able to see a couple of them before submission, which was a big relief.
I'd also recommend trying to get some shadowing/volunteer experience early, since I think it will reflect positively if you can say you've been committed to getting to know the field for a few years.
I'm happy to share my stats + experience if you would find that helpful. It's really good that you're thinking ahead!!