In case of volatile substances evaporation could be the good technique because different substances have different boiling points.termed as .The chemistry of a substance determines which process is to be used for separation.For solid substance we generally use crystallization.For large insoluble solute particles we use filtration.Solvent extraction is used to separate two miscible liquids.Distillation is a efficient method of separation of two liquids.For other methods visit this link.Methods of separation.