After you've checked over the tires and braking system lower the vehicle back to the ground and start the engine. It is easier to check for exhaust and fuel leaks with the vehicle idling. Raise the vehicle all the way up to where you can walk under it comfortably. Walk under the vehicle and check the whole exhaust system for any leaks. An easy way to do this is to have a coworker or partner hold their hands over the exhaust tip/tips while you listen for leaks. This way the exhaust fumes are forced out of any leaks and are easily heard and found You can also use a smoke machine to check for leaks, which is demonstrated in the video below. Check the for any fuel leaks too while you're under there. Fuel leaks are usually easy to sense because the scent of gasoline is very strong. But even if you dont smell any fuel, visually inspect the fuel lines from the fuel tank all the way to the engine for any thing that may cause a future problem with the vehicle.