A very common misconception is whether you need to buy optional liability waivers when renting a vehicle. The optional liability waivers could be expensive and a pushy salesman may try to tell you, you cannot leave the lot without it. Optional collision-damage waivers represent a "significant" source of income for car rental companies. So there are a few ways to protect yourself in these car rentals.
1. Understand your state or province's laws. For example Florida statutes say that if you're renting a car for less than a year, the owner is the car rental company is responsible for insurance. There are no such laws in Canada.
2. Understanding your insurance policy. Most insurance policy will automatically cover a replacement rental and you will not need additional waivers.
3. Check your credit card company. Some credit cards offer rental car insurance as a part of the deal with membership. Make sure you ask before renting.