Writer's Fallout Shelter

I'm in the middle of writing a story[some of it is on here] about some real life experiences I've been involved with and I was wondering what the limits are on how truthful the truth really is.

The reason I ask this is because I just finished reading Augusten Burroughs works Running With Scissors and Dry and I know he was sued big time for writing about real life incidents, that the ones included claimed he had slandered their family name.

One day I intend to have a novel published and want to include some of this within the story and wanted to know how much truth can actually be in the story? Must only names be changed?