The first is thing to avoid in the process of washing your car in direct sunlight, because the car gets hot and the water evaporates on it leaving marks behind. Make sure that your car is cool before starting. Wash in a shade or any time of the day when the sun is not blaring down. Start by taking some car shampoo on a bucket and wash from top to bottom with a microfiber wash mitt or a soft sponge. Avoid pressing too hard on the paint, let the soap do the work. Remember to wash on spots like behind the fuel door, wiper blades, and the door jams. Make sure to avoid dish soap and thin towels as it strips wax and cause hairline scratches.