My area of experience is traditionally published picture books, meaning a publisher who pays you for your work and handles all the design, illustration, distribution and marketing. If you're interested in self-publishing, I suggest checking out Harold Underdown's resources on that topic.
The more you write, the better you will get at it. But also, ideas need to be fleshed out, or they don't become stories. I talk to a lot of folks who tell me they have an idea, but only a few have actually written it down and tried to turn it into a manuscript. Also, getting published is partially a numbers game. You need to have a good idea, crafted into a well polished manuscript, but it also needs to be the right story at the right time. Kate Messner has a great post here, where she talks about how she has about 1 idea a day, but only about 100 of those ideas will make it into her notebook, and only 20 of those will become manuscripts, and only 8 of those will go to her agent, and only 5 of those will go on submission, and only 1 or 2 will become published books. That means, if you want to get published you need to write a lot!
The more you read, the more you will understand what makes for a good picture book and what is currently being published. This means reading picture books published within the past 3-5 years – no older or they won't reflect current trends. If you find a book that resonates with you, try copying out the manuscript. You'll notice so much more about it when you do! Examine the structure of the book – what type of plot does it have? How does the author build excitement or get you care about a character? You can pick mentor texts to study specific elements of writing. ReFoReMo and it's successor March On with Mentor Texts are great ways to find good mentor texts to look at. The archives have lots of great suggestions, too.
Find others who are on the same journey as you! It is very hard to be persistent enough to succeed without the encouragement, networking, and critique of like-minded people. SCBWI is a great place to start, and where I found my own community. I highly recommend seeking out those who are at a similar stage of their publishing journey to you, and forming critique groups. You can hone your craft, make friends, and receive encouragement, because making a book is a long-distance marathon, and it requires a lot of time and dedication. Getting there alone is tough to do.
It is hard to see the flaws in your own work. Find others who can help you learn and grow in your writing. This is invaluable. Also evaluate the opinions of others carefully. It can be easy to either quickly reject other's advice, or to apply everything you hear. Pay attention to what bothers people if more than one person points out a specific problem with your story, then it's probably an issue. But you don't have to use the suggested solution, you can find your own! Find those whose opinion you trust. You can form critique partnerships or groups, or you can pay for feedback from reputable editors, often at conferences for a modest additional fee.