Start here:
Amélie Lamont’s Guide to Allyship
Confronting microaggressions:
This outstanding article offers a framework (and suggested language) to help targets, allies, and bystanders in confronting microaggressions:
Sue, D. W., Alsaidi, S., Awad, M. N., Glaeser, E., Calle, C. Z., & Mendez, N. (2019). Disarming racial microaggressions: Microintervention strategies for targets, White allies, and bystanders. American Psychologist, 74(1), 128. [full-text access through Gitenstein Library][full-text access on the open web]
Tips for being a good ally:
Apologizing when you make a mistake as an ally:
Even allies make mistakes. When they do, the apology matters. Here's one helpful article about appropriate apologies.
And a helpful video: