Pretty simple strategy really -

• Make it animated (original GIF artwork was somewhat rare still)

• Target a built-in audience (people who love New York)

• Make it entirely original (no parody of other brands/characters)

• Combine humor and practical advice (a combination that does well)

• Draw it in black and white (cheaper to print)

• Plaster the name of the series on every single page so potential buyers can contact me (It has to be on every single image because they WILL get separated on the internet)