Basically what scholarly journals do to maximize exposure and find content (authors and papers) is indexing them in data bases and directories, whether they are recognized journals, or new and open access.
At a second level, although it’s also important, is to create a database of authors, scientists and professors of the journal specialty field, either searching directly for them when they publish in other journals, or using their database of subscribers/readers.
Finally there is the Internet and social networks, creating their own pages for being followed by scientists, but I think it is still to be developed. Some journals make their call for papers in their own portals and even in specialized websites; undoubtedly it’ll be part of the future.
http://gaudeamusacademia.com/forum/topics/what-else-can-journals-do-to-maximize-exposure-and-attract-conten