Locals/regular visitors, can you tell me anything about gang culture and gun crime in Chicago?

I recently watched a documentary on one of the BBC channels which claimed that Chicago has some of the worst gang crime in the US. Now, while I am sure that they focused on the worst of the worst for the sake of viewing figures but the statistics were pretty terrifying. I am interested to know what experience you have of Chicago as a local or visitor and what advice you have for staying safe when exploring the city. Are there any areas you would advise steering clear of completely for example? Basically, apart from basic common sense, what advise do you have for someone visiting the city for the first time? On the flip side, what positive recommendations do you have (ie must sees etc)?