How does one do it? Wouldn't we all like to know!
Beyond the obvious--competent writing, correct grammar, usage, and mechanics, a compelling story or subject--there are as many tips available from a simple internet search as there are stars in the sky. Some samples:
Harold Underdown gives us a list specific to children's literature.
A hard-hitting, frank assessment from Rachel Funari at PoeWar Writing Career Center.
Someone calling himself 'I, Brian' at SFF Chronicles, and who berates authors for using pseudonyms when HIS full name is unavailable on this site, gives some frank and cruelly humorous insight into the slush pile at a large publication. He's absolutely correct on many of his points, but one thing he neglects to mention is that authors absolutely MUST read and adhere to submission guidelines for each individual market. "Industry Standards," such as Courier typeface and paper-clipped manuscripts, are only industry standards as far as the market demands them.
For novelists, this article's author, C. Patrick Schulze, explains the importance of a good query letter in rising out of the slush pile.