Market. In order to sell your work you need to keep informed of markets and current publishing trends. Study magazines you are interested in writing for and become familiar with their style and content. Also look at what is being promoted in bookshops and that is favoured by certain publishers. By being aware of market trends and requirements, you will be better able to style and pitch your work.
Notebook. A notebook for recording ideas, sources and thoughts is essential and wherever you go you should always aim to have a notebook with you. Ideas can strike at the unlikeliest of times and, if not jotted down, can quickly be forgotten. Also when inspiration flags, your notebook could give you some useful ideas to work on.
Originality. In order to make your writing stand out, you need to consider how you can make your work special. What new angle or perspective can you bring to a subject that makes it different from others? Be original. Look for twists and fresh approaches and this way your work will stand more chance of being noticed.