The way most people get published in good magazines is to publish first in crappy magazines, or at least publish somewhere. That way you have a publishing history which will help get them to pay attention to your submissions. Whether you publish elsewhere or not you need to learn about query letters/cover letters, find out the submission guidelines of the magazine and adhere to them strictly, and generally learn how to present yourself and your images in a professional manner. Photographer's Market is a good place to start, but I would read everything you can find on the subject before submitting because first impressions are everything.