Where can I find good research assistant opportunities as an undergrad?

I’m a sophomore studying Computer Science and I’m interested in eventually pursuing research/graduate school in AI/ML. I’m looking to become a research assistant and get meaningful research experience that would actually strengthen my CV, rather than just doing something that gives me the title of “research assistant.”h
For those who have experience with undergraduate research:
Where do you recommend looking for RA opportunities?
Are there specific websites, programs, labs, professors, or organizations I should be checking?
Are there opportunities for undergrads to work remotely with professors/researchers at other universities?
What would make an RA position genuinely valuable for future grad school applications?
Is cold-emailing professors actually effective, and if so, how should I approach it?

I’m especially interested in CS/AI/ML-related research, but I’m open to other areas if the experience is strong.