New York City becomes “NYC,” Los Angeles becomes “LA,” etc. Big deal, acronyms are easy. But what about long city names that don’t lend themselves to acronyms? Does Cincinnati become “Cinci”? Does Chattanooga become “Chat”? How about your own long-named town?
Edwardsville becomes “E’ville” and Glen Carbon is normally shortened to “Glen” (with, of course, the combined area being noted as “Glen-Ed”)
Cincinnati normally is shortened to “Cincy”
I’ve seen Beavercreek abreviated to “B’creek” in print although the locals refer to it verbally as “The 'Creek” and the same for Miamisburg (“M’burg” and “The 'Burg”).
In some cases, the city gets its nickname, rather than a shortening. Thus Boston becomes “Hub.”
Different papers have different conventions. Sometimes, cities that regular readers of the paper are familiar with may be shortened, but it isn’t AP style and in my experience it’s usually avoided if possible.
For example, in the top 50 U.S. newspapers, for the Minneapolis bridge collapse, many use “Minneapolis” in the headline. A few use “Twin Cities.” I’m of the opinion that the two using “Minn.” were using the AP Style abbreviation for Minnesota, and not a shortened version of the city.
If it’s their home city, many papers will just use “City,” as in “City to receive funding” or “City police arrest 17.” Can’t get much shorter than that. For other cities, you either shorten up the rest of the headline to get it to fit, or you find a way of writing it where you don’t need the city name (and perhaps include that information in a subhead or something, if possible).
As a former resident of Cincinnati, I’ve seen it abbreviated in newspapers as Cincy, Cinci, Cinti (most formal, for some reason), and rarely, “The 'Nati.” I don’t think there’s a standard, but it was avoided when possible.
I also lived for a time in Columbus, and while I never saw it in print, it was sometimes colloquially referred to as either “C-town” or “C-bus” by us college wannabe hipsters. While I doubt that would have made it into the Dispatch, I wouldn’t have been surprised to see that in some of the smaller newspapers.
Indianapolis is most often Indy. Naptown sneaks in sometimes, but the city is no longer as peaceful or boring as it was.
Valporaiso is Valpo.
New Palestine is New Pal.
Pendleton has prisons, so it would be impolite to call it Pen. 
Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch becomes Llanfairpg
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Quite rampant in the Cleveland metro area. Rule of thumb: the second word of the name of two-word affluent suburbs can be dropped, especially in informal “insider” type articles.
Shaker Heights: Shaker
Bay Village: Bay
Rocky River: Rocky
Pepper Pike: Pepper
Moreland Hills: Moreland
Gates Mills: Gates
Hunting Valley: Hunting
Waite Hill: Waite
You get the idea.
“Shaker”, “Bay” and “Rocky” can usually be used alone in headlines; it’s less common to see the names of smaller suburbs shortened outside of article text.
The key is “affluent”. Nobody drops the “Heights” from University Heights or Garfield Heights.
Or, of course, Cleveland Heights. But the area in general (the eastern 'burbs that end in “Heights” is often called “The Heights.”
Schenectady is usually “Sch’dy.” Most people use that instead of the entire name whenever possible.
There are a handful of cities in the US that have recognizable abbreviations. Minneapolis, for example, has Mpls. Philadelphia has, of course, Philly or Phila., and I’ve seen Pgh used for Pittsburgh.
Where I live, E-town and E-ville are used for Elizabethtown and Elizabethville, respectively.
Robin
But of course, people in other places often refer to Chicago as Chi-town, although no one who lives here would be caught dead saying that. I cringe to write it. Probably similar to Frisco or San Fran for the folks who live in San Francisco.
Newspapers often use just “City” in headlines, too. It’s a short word, and it’s generally pretty clear that this refers the the local city.
It can be used to refer to the city as a whole, city elected officials, city government, city departments, etc.
“City traffic congestion getting worse”
“City to prosecute dog owner”
“City asks for State aid”
“City to enforce parking restrictions”
We have a lot of places around here whose offical names are “Township of Whatever” to distinguish them from simliar towns that are just called “Whatever.” The newspapers simply write “Whatever Twp.”
My town is actually a borough, and the only one in the newspaper’s area, so sometimes they will say “Borough passes tax hike”. It’s only two letters shorter, so it’s usually just done for variety when there are two stories about the same town on the local section front page.
The local free weekly artsy fartsy fish wrapper normally refers to Albuquerque as 'Burque. (pronounced BUR-KAY) Makes me cringe every time I see it.
The Nashville paper willl often call the city functions “Metro”. “Metro Public Schools”, “Metro Police”. The surrounding neighborhoods are often called by their county name “Rutherford School”. I live outside of Murfreesboro, which is usually shortened to “the 'boro”.
StG
Milwaukee is MKE (just like its airport).
Oconomowoc doesn’t get shortened mainly because it’s so fun to say!
Mukwonago often gets shortened to Muk.
Jacksonville FL = Jax, at least w/r/t most abbreviational circumstances (never saw it in a paper headline, not having read a Jacksonville newspaper.)