My sign reads
No Soliciting no religious groups
If you haven't been invited
You aren't welcome
So go annoy someone else.
Pizza delivery guy cracked right up and one person stole the sign somewhere and I put up another one.
sEems to work though.
If particularly persistent you could disconnect the wire on your doorbell on sundays. They won't know it isn't ringing.
One grooming client I have has a daycare. Her sign says,
Babies sleeping, you ring the bell and wake them you get to come in and rock them back to sleep.