Some periodicals will send you one or more sample copies if you request them with an SASE with enough postage for the return (a few will ask for payment). Other publishers have whole issues or at least several sample articles available on their Website. In those cases, they may prefer that you study those. Some publishers will have a place on their Website to order sample copies. If there is nothing said on a Website about sample copies, you could write and ask for several copies (6 would be ideal) and volunteer to pay for them. Many writers' conferences also offer freebie tables where you can pick up sample copies for free. Read the samples cover to cover to begin recognizing the style, focus, target audience, etc. Take notes to add to their guidelines to remind you of any information you gleaned from the reading. It's a good idea to go back and read the sample copy(s) and the writers' guidelines before you start writing a piece for any one of the publications. Store your sample copies in boxes alphabetically by title so they are easily accessible. For access to sample copies for a good number of periodicals, go to: http://www.writing-world.com/basics/samples.shtml.