Understand the story. Read it in its entirety. Granted, you probably are familiar with the basic gist of it, especially if you are an editor for a small publication where you are both the managing and copy editor. The key is to read what your reporter said about the event, as this is the best way to get an accurate handle on what the best headline will be. You never know what angle she may have taken. For example, you may know that the Reds played the Cardinals, but did you know that the game was saved by an unlikely hero? That would definitely affect your headline.
Know your publication's specific requirements, as some may be a bit more liberal with what you can say. For example, look at a "New York Times" sports headline versus an ESPN.com headline. The former is dry and to the point no matter how momentous the event, whereas the latter lives and dies by the pun. Once you know what your publisher and supervisors want, you will then be able to better craft a good sports newspaper headline.
Use key words in your sports newspaper headline. Search engine optimization (SEO) styles of writing emphasize this in order to bolster readership, but even traditional print media outlets need to cover as much of the basics as possible in their sports headlines. For example, if a game was won on a miracle play, you want to note the significance in the headline. But simply writing "What a Game! Cubs Win!" won't do. Instead, opt for "Miracle at Wrigley: Cubs Outlast Cardinals 10-9 in Extra Innings."
Review the headline after spending a few moments away from it. Ask yourself if you would be enticed and would want to read the story. Remember, in a sense, you are responsible for your reporter's readership. It's not fair if he has written a great story only for it to be ignored because of a lackluster headline on your part.
Showcase an angle that readers haven't thought of yet. Sports fans are an esoteric bunch, and it's a safe assumption that many already know the results of the events. What feature of the headline will make them want to read more? The trick is to say a lot with a little, a Hemingway-esque touch that will serve you well in terms of writing a good sports newspaper headline.