Recently, I was called an ally and that got me thinking about how anyone can be an ally to any marginalized group... And I've learned this from others. I claim no credit.
First, PLEASE LISTEN. When people are speaking, the rest of us must listen. This is a time to put aside what we 'think' we may know to REALLY learning from the very group we wish to support.
Second, the ally must out aside the systemic narratives that have been enforced by society for generations on the particular group. In other words, just because you've been told something, don't think it's true.
Oftentimes, we human beings will have an untruth in our heads and will 'see' what we want to see. Experience what we WANT to experience. Remember, DON'T BELIEVE THE HYPE.
Thirdly, please, Please, PLEASE listen to experts/researchers/social activists who have that group's interest in mind. We have a historical issue in this country that we take what somebody has said about a marginalized group in the trappings of 'science' when we know that the academic community is pulled and pushed by prejudice, racism, bigotry, xenophobia, and wilful ignorance like any where else.
Lastly, please do your own research as well. Once those from the group invite you in, make sure to take the information they give as part of the foundation of your own prejudices'/biases' undoing.
As you learn more with what you've been given, you will fortunately learn your own faults, prejudices, and biases as well. It's uncomfortable, often frightening, but very VERY necessary. You will become better as a person. Your future self will thank you. Not everyone can do this. Being willfully ignorant is a shield for many people. Don't be cowardly like them. Be better. Do better.