Provide a self-addressed, stamped envelope for the editor to reply. The publication will either accept your proposal and provide specifications including things such as length and deadline and invite you to submit on speculation, or they can reject your idea, and will sometimes tell you why. Some may choose to ignore you altogether. Following up rarely changes anything. An article has a beginning, middle and end.
Many people ignore that fact.
Use an opening that captures attention immediately. Just ask your customers. The middle should contain coherent, supportable points. The ending should be a summary of the article's key points and a call to action. Always submit a photo with the article, because it enhances the piece and increases your memorability.