Especially if you're cis, get over yourself and what 'being the kind of person who cares about trans-folks' rights' means to you. Accept that caring about things matters a lot less than actually helping a real person. Your thoughts don't change the world if they don't translate into actions.

If a buddy comes out as trans (and has a similar gender/size to you), ask if they'd like some of your clothes, accessories, or whatever. This is, IMO, one of the most wholesome ways to support someone. When folks do gender-y stuff, rebuilding a wardrobe can be hard, time-consuming, and expensive. Going shopping with them (especially if you're similar genders) can also be fun and helpful.

Be a little careful, though! Sometimes, trying on clothes can feel a little dysphoric for someone. It's hard work to figure out if something is flattering, especially if someone is getting used to seeing their body differently. I try to avoid pushing my opinions on something onto someone unless they ask. If something looks really good, I might tell them that in a general way, but I avoid highlighting specific areas of their body unless I'm 100% sure it would be validating and wouldn't come off as patronizing or whatever.

It's usually easiest to just be a little quieter during 'trying stuff on time', and then do something that's comfy after and doesn't involve a lot of thinking about bodies.

It's also good to give them things and let them try them on at home, and then get back to you another day. They probably won't want everything, but having that space so their can process emotions or whatever, if they want it, can be a considerate thing.

Remember: you don't have any right to see or evaluate how they look in stuff. You're just here to help *them* feel comfy doing that for themselves.

Help your trans friends get stable, safe, comfortably-paying jobs.

There really aren't any universal suggestions here, but do your best to help out if ya can. Remember that just because your workplace is nice to you doesn't necessarily mean that everybody there would treat your friend well.

Financial instability can exacerbate a bunch of other issues, and it can sometimes be hard to find a 'boring office job' that isn't full of microaggressions. Not to say that everybody should have a boring office job, but IMO, those are powerful tools for stability.

You got buds who are kind of "medium" about "the whole trans rights thing"? Talk to them.

Be soft about it, at first. Trans folks have every reason to get mad, but if you're just being a good ally, please do not be mad. It will make things harder for your friend, and people usually learn better when they aren't scared to say something 'wrong'.

In my experience, a mixture of education around basic biology (particularly around how hormones work) combined with establishing what reasonable boundaries are (ie "it's rude to ask someone what their genitals are like") works best.

Other tips cis people usually haven't figured out is to usually gender by 'choices' rather than by 'appearance'-- focus on things like makeup, clothing, shoes, etc when guessing for a stranger. Or, just ask. Sometimes, people are 'medium' because they don't feel confident in navigating social situations, and if they're too uncomfortable to ask someone's pronouns, you probably won't be able to change that in a single conversation... But giving them tips on how to avoid misgendering someone is usually appreciated, if they're interested in being nicer to their fellow humans.

However, sometimes people are 'medium' because their friends are assholes and they don't want to stop being friends with assholes. If your buddy is like this, encourage them to get new friends. If they refuse, distance yourself a bit. You can check in with them a few times a year, maybe, but if they're still being weird about it, they're probably not that cool anyways.

Sometimes people take a long time to 'come around' to something, though, and if you think they might, they may find themselves in a position where they are hoping to talk to someone they might've disagreed with a few years ago. If you're trans, I wouldn't encourage you to do this because, honestly, it seems exhausting and unsafe. But, if you aren't, it can help prevent someone from retaliation over them deciding to be nice to people.

Also, their old (transphobic) friends might see how much of a better time their friend is now having, which can be a pretty persuasive situation. ...Not that you really care much about their old transphobic friends.

Engage in politcs in ways that make things better, especially if your trans friends say that a policy matters.

If they're worried about something and there is a call for public comments, leave one if you can. If there is something on your ballot, make sure you go vote. Equity is more than just trying to improve a broken justice system, but a broken justice system will continue to produce inequities and injustices.

You might be afraid to use your 'real name'-- if you are, why? Is there an actual, specific threat you're worried about? If not, and especially if there isn't an you're just an ally, lend a little bit of your privilege. Any consequence you feel as a result of supporting someone's safety will be much more dilute than the actual threat to someone else.

In my experience, the biggest impact is being aware that a web search can confirm that I do publicly support trans rights, and that I should remember this if someone comes out of the blue and says something weird at me. But honestly? Nobody has, and I've been public, about supporting this stuff for almost a decade. Don't sweat it.

Invite friends with estranged families to join in with your own holiday stuff. Even if a lot of people might not be able to make it, the ones who can are usually really glad to have something, since it might be the only holiday party they attend that year.