People think their information is protected while it is sitting in their homes, which is not true. Therefore:
Always shred your bills, credit card offers before disposing off
At home try to mantain a clean desk policy, to ensure your bills and other information is not lying around in the open, which makes it easy for visitors to pick up
Never carry your SSN/SIN card in your wallet/purse
Never provide your SSN/SIN numbers to anyone besides your TAX Agency, all other agencies need it but it is not mandatory