You first need to make sure you have room to work under your car. You probably will need to jack it up if your working on a car or minivan. You may have enough room in a truck where you wont need to do this. Now make sure the engine bay is cool enough to work in so you wont burn yourself. Its better if the oil is still warm so it will drain out more completely. Waiting 10 minutes after the engine is turned off (From operating tempature) is ussally good.