How can I stop being rude?

The way to stop rude behavior is to quench the behavior that starts it. Rudeness often comes from a displeasure with setting or other's behavior. You need to be mindful of this aspect and allow yourself distance if you need it. I know it sounds cliche, but I always have to remind myself to think before I speak. That way, I can know if I am coming off harsh to someone, though sometimes I can find myself drifting off of topic. This is common for many individuals who have trouble overcoming their attitude. It is a long path that also is paired with sharing boundaries and making sure to keep calm.

Try to see how other people feel and walk a mile in their shoes. This way you might be more sensitive to other people feelings.

You could start putting yourself on the other people's shoes. Everyone is fighting a hard battle just like you, so there's no reason for you to don't treay people with kindness. Once you start doing that, you won't want to stop, just like happened to me. I used to yell at people for literally anything, even when the mistake was actually mine, not their. I think that if every body treat the other like they would like beeing treated, many of the world problems wouldn't exist, if not all. To summarize, you won't do any good making people feel bad, but you can do much good by making them feel loved!

Think before you act and/or speak. try doing small acts of kindness, say hi to random people, smile. open doors. being kind can become a habit.

Well that depends on who you're interacting, the situation, why you're acting rude, etc. For the sake of this question, I'll just assume that you're feeling that you're generally rude to everybody, and if that's the case, I guess have some empathy for others? Perhaps by putting yourself in someone else's shoes, you'll see that your words/actions could hurt someone else.

Just as simple as you can guess. Treat people with respect, think before you speak and behave like you would like others to behave towards you.

Think twice before making a comment. Everyone is entitled to their opinion. However, not every opinion can be well received after it has been spoken. A lot of time even when you are stating the facts, others may perceive what you said as a persona attack. There is an internet meme, "if you can't say anything nice, please do say it". There is some truth in it. If you have been called rude often, it will be nice to be aware of what you are trying to say. Often when you are doing a review on the sentences in your head, you may find out they sound judgmental. Then keep them to yourself only.