what best concentration .dispose()

this something i have never entirely grasped .net repremand concentration .dispose() method.

say i have something like

public category someclass()
  servant somemethod
    ' things confining adult resources
  finish sub
end class

public category mainapp 
  low _class new someclass
  _class.somemethod()
end class

in cases good use exercise dispose method, should there?

if box each category should have dispose slight (which stomach feeling says shouldn't) classes should? i have always guess anything competence tie adult apparatus (i.e. connection, datareader etc) should have .dispose() unallocate resources.

also make job calling .dispose() method?