Depends on the message you wanna convey. Like -kun, for instance. Typically you see that used with men of close familiarity. -sama is like... [How to phrase this]

-Sama is one of the highest respects you can give a person. Sorta like equating them to a god. Or a goddess~! [Nodding] Every goddess deserves a -sama behind her name. [But he's getting derailed here, isn't he?]

-chan... Most commonly for ladies. You can see it as the equivalent of -kun. Not that it stops people from using it with men, but typically only kids do that. Or close friends. Or if you wanna piss someone off.