You must write articles that contain information that is useful and educational to the audience. Often giving away little trade secrets will increase your chances of getting published and build your credibility with both the editors and the reading audience. Be persistent - Not pushy Publishing is not for the weak of spirit. Put your pride aside and resist the natural tendency to be hurt when receiving a rejection. You will receive your share of rejections.
Every writer does.
When you receive a rejection write a polite thank you to the editor for considering your work. This paves the way for future submissions. Consider calling and asking politely what you may do to further your chances of being accepted into their publication. Never, ever be rude or pushy with an editor. This will only insure that you will never be considered for future opportunities.