Philipp Lenssen has an excellent write up on How Google News Indexes. He explains how news souces get indexed, which sources to get place in the Google News home page and when news sources collapse into clusters.
Google selects the sites themselves to put to their page or sometimes you can ask them to put your soure. Google News sorts every story to put in a cluster. If fifteen sources pick the same story( even if the stories mismatch to some extent), for instance, Google will display them in a cluster of almost same stories..
"Google News honors sites that break the news." Google puts the news breakers on top spot. So to get your site indexed in Google News make sure that you break the story. Moreover, you can make it to Google News homepage if your article is an original one and falls among the "most popular topic clusters in a given section (like Entertainment, US, World, Business…). "
Besides, if your article carries an image preferably middle-sized JPG images, Google News may show a thumbnail of it. "Google News also powers certain News Alerts. As many people subscribe to News Alerts on their own name, or their company name, having a story being indexed in Google News often means the CEO in question will read it."