Crime Prevention Tips?

My husband & I want to do all we can to keep our neighborhood clean & safe. So far, all we can think to do is call 911 every time we see something unsavory. Does anyone have any additional crime prevention tips?

(On our block, we are having issues with prostitution, drug sales, drug users, and gangs. The drug users seem to cause the biggest disturbance as far as noise, fights, littering, minor thefts, & car break-ins.)