Flux lines always follow the paths of least resistance or in magnetic terms, path of greatest permanence (lowest reluctance).
Flux lines repel each other if their directions of flow are the same and can never cross.
Flux lines always travel from the nearest north pole to the nearest south pole, in a path that forms a closed loop.
Flux lines will normally always move in curved paths.
Flux lines always leave and enter the surfaces of ferromagnetic materials at right angles.