“I don’t answer questions” is a powerful statement, as you have a right to remain silent. If an officer attempts to stop you on the street, you can simply ask them if you are being arrested or detained. If they say no, you can walk off in silence.
If you are detained or arrested by police, they have to immediately inform you as to why you are being detained, then immediately provide you with your rights, which include the right to silence and the right to speak to a lawyer of your choice. Lawyers will advise you NOT to speak to police.
Courts are forbidden from associating silence with guilt or suspicion. Not providing a statement to police is usually in your best interest as anything you say can be used against you as evidence of the offence. If detained, you should give your name and date of birth, but it is typically not recommended to say anything else.
Police can continue to ask you questions and will often use a variety of techniques to try and get you to speak to them, even after you have told them multiple times you do not wish to answer any questions. You can simply reply that you are asserting your right to silence, but understand that does not prohibit them from asking questions, so be prepared to offer that reply over and over.
If you are pulled over in your car under the Highway Traffic Act, police do have the ability to ask you questions you are compelled to answer. These questions MUST be restricted to the driver and must be directly related to the sobriety of the drive, the licensing and insurance of the driver and ownership of the vehicle, and the fitness of the vehicle. Any other questions can only result from a proper arrest or detention, and must follow the same protocol listed above.