How does one stop a neighborhood from becoming crime ridden?

Once a neighborhood is going bad (high crime rate), is it too late to stop the process? Should neighborhoods have covenants that state all houses must have alarm systems? Would posting video cameras outside the home deter crime? Would charter schools help retain family structure and limit dangerous influences since parents want their children to attend? Would abortions clinics in deteriorating neighborhoods lower the crime rate as Freakonomics suggests? Would penalizing crime ridden neighborhoods by cutting the resident’s access to cable to make them read more (and possibly lower crime)? Should the police create checkpoints for all points of entry for a neighborhood after 10 murders happen in 6 months for a 5 mile radius? I would like to see constructive answers to see if we could what we could generate something smart and productive that people could really use. Obviously not all of my questions could be implemented, but I want to see what we come up with.