Pretty much the way it's always been done. Surf the webmaster boards and resource sites. Oprano and AllOfEm come to minfd there
and try and glean as much knowledge as possible about where to submit and what not. In the meantime use sponsor content and build a bunch of TGP galleries and double them up and use those pages to also build free sites at the same time. Once you've got a little money coming in then sink some or all of it back in to getting non sponsor content and rinse and repeat.