Reaching out to PIs?

[queerorpheus]

I've seen a lot of things online that now is a good time to start reaching out to PIs but I really have no idea where to start with that. I have a list of schools I want to apply to and PIs at each that I'd be interested in in working with. Is it typical to reach out to several PIs for each program or just one? I have a general idea that I should introduce myself as an applicant that would be interested in working in their lab, but how much should I talk about myself/research vs. just an introductory email? I don't have a lot of guidance on this so anything helps. Thanks y'all!