A/au/du/de: in, to, or from a place

In or to a place: à/au/aux/en (with hints)

From a place: du/de la/des/d' (with hints)

In, from, or to a place: à/au/aux/en vs. du/de la/des/d' (with hints)

To/in the north, to/in the south of: au nord du, au sud de (with hints)