To be a successful freelance writer you need to have several story ideas up your sleeve, and write several pages of decent copy, and interview people however, it is also extremely important to have those ideas to start with, so you can turn your ideas into a good story.
Also when writing your story avoid making some unintentional comment, an unless you are writing an opinion piece also refrain from making your own opinion known as your opinion is not warranted and your readers will be displeased with you and your opinion!
And even for the most experience and inexperienced writers allow a cooling off period before you edit and re-edit your article/story.
That is after you have written your story, put it out of sight and out of mind for a couple of days, and then read it again at least twice and you will find there are many errors that need fixing.
Fix and then re-edit and put away for another day and then re-read and fine tune your editing and you should have a master piece ready for the Editor.