Follow the submission guidelines to a tee. For a small journal Like Pocketry it will be the difference between getting published and knocked back. For larger journals I suspect they won't even look at your work if you haven't bothered to take the time to read their submission guidelines and follow them. If you can't be bothered to do your homework, why should they bother to read and then publish your poems?
A publisher creates submission guidelines to streamline the task of assembling a journal. As you can imagine, a lot of work goes into creating a journal. When you follow the guidelines you make the editor's job of choosing you easy. With hundreds of submissions and many pieces to publish there simply isn't time to go back and forth with every contributor.
Pay attention to simple things like document type, font type and size as well as requirements for contact details, author bio, photograph size and format. Get the details right and then your killer poem will shine.