Using headlines, subheads, etc. from your sample content taken from competitor magazines, develop rough explorations of organization and hierarchy of information on your covers. You are not exploring cover layout here, just pairings of type style, size, weight, etc.
Each cover will eventually have a primary feature article, which matches the cover image, and list at least two other sub-article headlines plus a teaser for one other type of feature info (such as a recipe, top ten list, info graph, etc). Develop at least 3 directions for the hierarchy of info on your covers, trying different type combinations to achieve hierarchy in different ways. Each direction should correspond to one of your masthead directions. At this point, you may include FPO (for placement only) images on your covers. These can be sketches, temporary stock images or roughs of the images you are developing.