The swift reporting and abatement of graffiti discourages future vandalism, so when you see graffiti report it immediately. Graffiti Protective Coatings and the City of Tucson have a smartphone application for reporting graffiti. MyTucson is a free download on the iOS App Store and Google Play for Android.
You can also report graffiti by emailing email@example.com, or calling (520) 792-2489 and choosing option 1.
Watch the University of Arizona Public Service Announcement about the MyTucson app.