You should periodically take an inventory of items in the trunk of your car. Here are some suggested trunk contents:
Spare tire - A spare tire is typically located in the trunk, under your vehicle or on the tailgate.
Vehicle jack - Depending on the make and model the jack is commonly located near the spare tire.
Tire tool (lug wrench) - The tire tool is typically located near the spare tire or in the trunk.
Water - Water is used for: 1. For Hydration, 2. For first aid, 3. For Hygiene, and 4. To refill your radiator.
Blanket & Rain Poncho - A blanket and a rain poncho are "must have" items.
Flashlight - Keep a flashlight with fresh batteries on-hand.
Gas container - A gas container is useful for obvious reasons but often overlooked.
Tire repair materials - The link provides information regarding inflators, sealants and air compressors.
View the related links below for a more comprehensive listing of things you should have in your car.