Reasonableness: a good local custom must be reasonable i.e. consistent with the principle of justice.
Conformity with statute law: a local custom must be consistent with statute law. This is because parliament is the supreme law making body, hence its law is superior.
Observance as of right: a good local custom must have been observed openly and as of rights i.e. not force or stealth nor at will.
Immemorial antiquity: a local custom must have been observed since time immemorial. Time immemorial means no living person can attest as to when the custom did not exist.