I think the best tip for any writer is... READ. Read. Read. Read. The more you observe how different authors write, the more you can learn to write better on your own. And don't just stick to one genre or style-- actively seek out different authors and try to dip your toe into genres that you don't already enjoy.
As with any other skill, you'll get better with practice. Don't expect your first few stories to be perfect. They might not even be good! And that's okay! Don't be afraid to write some bad stories if that's what it takes to build up your skills.
Study. If you're able to, try to take a creative writing class of some sort. Watch videos online. Read blog posts. Do writing workshops. Gain an understanding of story structure. Learn how to make strong, likable characters. There are endless resources out there to help you learn how to be a better writer. Seek them out.
Lastly, remember to plan ahead. I cannot begin to tell you how many times I've come across beginner writers sharing novels or comics where they obviously have no idea where they're going. You don't have to have every single beat planned out from the second you come up with the story, but you should at least have an idea for the beginning, end, and a few points in the middle.