You don't need a car in Calgary itself as they have decent transit.Your credit card should have the equivalent of CDW and your own auto insurance should cover it. Your credit card comes with information you should read about car rentals. Also check with your insurance agent about any specifics. Make no assumptions. Check Expedia.ca for an overview of prices. You can bid on Priceline.com. You should also take a look at Hotwire.com.. The general thing is to avoid any extra charges if you can as they are all profit centers for the rental company, from insurance, to fuel to GPS.