An LGBTQ ally is a cisgender, heterosexual person who uses their privilege to support, protect, and aid people who face discrimination or other hardship because of their gender and/or sexuality.
Learning how to be an ally is a process. It is important to realize that we all make mistakes, we all have different privileges which make it hard for us to fully empathize with others, and we are all learning. When we understand this, we can admit our mistakes, accept correction, and grow as allies.
Here are some important first steps for new allies:
Including your pronouns when introducing yourself, on email signatures, and on social media. When cis people normalize sharing pronouns, it makes things just a bit easier for trans folks.
Speaking up when others use anti LGBTQ slurs, even when no LGBTQ people are present.
If you can, donate to LGBTQ organizations and individuals.
Read up on race allyship, dis/ability allyship, economic allyship, etc., and commit yourself to allyship in those areas as well. For white LGBTQ allies, remember that LGBTQ allyship includes allyship to Black and other LGBTQ people of color.
Make it known among family, friends, and coworkers that you support the LGBTQ community. If you are in a conservative area, it is understandable if this makes you nervous. Be as cautious as you need to be, but also remember that you will always be safer than your LGBTQ neighbors. If you are a Christian and working on being an ally at church/among other Christians, be prepared to make biblical and theological cases for why you support LGBTQ Christians. Do not refer anti LGBTQ Christians with questions to LGBTQ Christians.