The "Rule of Thumb" I was taught, is...move to a key at least 2 sharps or flats from the key signiture you are currently in.

A move from C to the keys of F or G does not "work" because the transitional keys are too similar..but a move to D or B is "magical" to the ear.

My rule of thumb is the same thing CatsPHiddle is saying.

Sincerely,
Gargoyle