If you're a cis person and you want to support the trans person in your life, just use their name and the correct pronouns and gender. Like, do it a lot. Especially when you're both around other people. Set the example. Correct people when they misgender and Deadname.

Seriously. It means a lot. More than you can know.

I have one coworker who always starts DMs in our work messenger with m'lady or similar. It's kinda cringe but it's so sweet. I LOVE it!

The airport parking shuttle driver somehow ma'am'd me like a dozen times between the airport and our car. Made my day. (Of course, that would NOT have made my day if it was "sir" or if I was transmasc.)

One of my favorite text messages I've ever received was my brother telling me how happy it made him to tell some guy in an airport bar that his sister has a PhD in math. Not that he likes my PhD but that he enjoyed calling me his sister.

Seriously. It means a lot.

People properly gendering you can make a trans person's day. It can also make the difference between a really awkward social situation and one that's survivable. It can make a crappy day better.