As a freelance writer, if you develop a good working relationship with at least a few editors, they will call on you time and time again when they need a writer for a specific assignment.
It takes time to cultivate such a relationship, but it's well worth it - for you AND the editor.
Many times, editors assign an article or story to a writer, but something happens and that writer is unable to complete the piece.
That's when the editor will call one of the many other writers he/she has worked with in the past and reassign the article so the deadline can still be met.
Just imagine getting such a call.
You've landed a great assignment without having to do anything new.
This editor knows from working with you previously that you will be able to handle the topic and you can be counted on to meet the deadline and turn in just the type of article or story he/she is looking for.
So once you land one assignment with a particular editor, meet the deadline and turn in a great piece.
Then, after that piece is accepted, have another article idea ready to pitch to this editor.
Also, if the editor calls to offer you another assignment, jump at the chance to do it - even if the topic of the article isn't something that is of particular interest to you.
Once editors know they can count on you, they'll call on you again and again.
So start developing a good working relationship with at least a few editors.
Try it!