Yeah, well, this one is hard to skip. If you want to be a writer, you've got to write.
However, I disagree with the old adage of "write every day." I know some writers just starting out get hung up on what they "should do," and everyone always says "write every day."
I don't write every day. In fact, there will be some weeks that go by when I don't write at all, especially if I'm not working on a specific project. However, that doesn't mean I'm letting my skills languish. When I'm not writing, I'm doing research, compiling information for upcoming magazine deadlines and prompts that interest me (on a side note, to find out more about what work different magazines are looking for and their deadlines, I definitely recommend The Grinder). When not writing, I'm listing story ideas, connecting with people on social sites and on my writer's group. I'm editing old works to send out or editing works written by friends. I'm reading and doing research. And I might be working on other creative endeavors, such as art or handicrafts.
So I guess an adage about what works for me would be "do something that progresses creativity every day." But that's quite a mouthful, isn't it? So, maybe: "Encourage your creativity every day." Okay, that sounds better.
2) Writer's Group
This one is essential - having someone else who will read your writing. My husband is generally first reader for most of my work, although I also have an online writer's group at Scribophile. I have friends who write all kinds of works, from nonfiction to fiction, from poetry to short stories to books to screenplays. Just as I feel it's good to have a diverse reading list, I think it's essential to have a diverse set of first readers - friends who will really tell you when your stuff sucks and who are skilled enough to tell you why. But - and this is important - I feel that it's important to have first readers who are also interested in pursuing the same goals you are. What I mean is that while the friends you've known since you were three might love to read your published writing, they perhaps won't want to read twenty drafts of a story before you submit it. Although I've never had it happen to me, I've heard about friendships that get worn down by too much "help."
The other aspect of a writer's group is editing. When I first got back to writing this past year, my skills were really, really rusty. Within a month of joining my group, by reading and editing a wide array of other writers' work, I learned more about writing than perhaps all my former creative writing classes put together. Writing is definitely one of those things you learn by doing - and half of writing is editing.
Just like writing, this is essential. It's like eating. You'll die if you don't eat, right? Because your body can't keep expending energy without some intake. Likewise, your writing will stagnate if you don't bring in new ideas, new viewpoints, new thoughts. A lot of reading I do nowadays is research (reading magazines I intend to submit work to, reading nonfiction books and articles for research for my manuscripts, scrolling online to keep up with the political and social climate), but I also read a fair amount of work by friends and I make sure to read something just for my own enjoyment each day. Right now, I've just gotten to Jonathan Strange & Mr. Norrell on my reading list. I've been meaning to read this since it first came out, and I finally bought a copy - and I highly recommend it, especially for historical fantasy buffs.
Okay, these are the three essentials. There are a ton more of sidebars to these three things, like questions about social media and how helpful it is, but I feel those are definitely extras. If you read, write and have your work critiqued by a writer's group, you WILL get published. It might take a while, and it will definitely take persistence, but it will happen. That's it.