Check tire pressure monthly
Properly inflated tires maximize safety, tire life and fuel economy. Tires that are 8psi underinflated reduce tire life by 10,000km and increase fuel consumption by 4%. That’s like adding 4¢/litre to the price of gas. Source
Once a month check your tire pressure using a tire gauge. On the frame of the driver’s door or inside your glove box is a label that says what the tire pressure should be. Most service stations have a free tire hose. For more details, check this link.