Historiann, Dr. Crazy, and Profacero have a series of excellent posts that Historiann has grouped under the title "Lessons for Girls."
I have one more: trust your instincts. By that, I mean judge people based on how they treat you, not based on hypothetical models of how people behave.
For example, as a feminist, I believe that women can and do help each other, can fight against injustices, can support each other against exploitation and harassment, and so on. But people are individuals, and individuals have their own flaws and their own agendas.
[I redacted the rest of this post because, upon reflection, it didn't fairly reflect the person I wrote about--sorry.]