The following are simplified forms of writer’s tips I have received over the years:
For amateurs: write every day, if in school or university take English classes. Join a writer’s group. Learn to accept constructive criticism. Read the greats.
For professionals: Don’t quit your day job. Don’t expect to earn a living doing it.
Get a communications or journalism degree and then you might be allowed to earn a living as an in house staff writer.
It is actually both what you can do and who you know or can get to listen to your pitch.
Lack of Help
There are ways to earn a living at it but people act as if letting you know what they are is more secret than people’s raunchiest sexual secrets or secret service classified information of their nation state, so good luck finding out.
Get a Mentor
It is possible to get mentors within professional realms and within higher educational organizations.
Move to New York City and meet editors and land a literary agent.
Move to Hollywood and get a job as an editorial assistant.
Figure out how to get invited to parties given by publishers, editors, literary agents and anyone else in the industry. Learn to schmooze for professional purposes instead of being designated as being solely for the entertainment of those in attendance.
Pitch using the Internet.
Attend conventions, professional writing groups, anything and everything you can try to get anywhere.
Nurture relationships with any editor who accepts your work.
Realize that many editors will not respond to even your best work for a variety of reasons.
Pay to get additional training.