Conduct all official business in English.
Stop giving them drivers' licenses.
Deny them any type of public assistance whatever, except emergency medical treatment.
Deny them standing to bring any type of claim in American courts.
Immediately deport, without a hearing, any illegal who comes to the attention of law enforcement.
Sentence those who who violate deportation orders or commit any type of identity theft and fraud (including presenting false IDs to any law enforcement agency, financial institution or employer) to hard labor working on the wall.
Deny them the opportunity to EVER apply for US citizenship.
In short, keep them living in fear and uncertainty about their future, and then watch how many start leaving on their own, or think twice about coming in the first place.
I like it.