Start by using a garage or shaded area. The hot sun will make proper car care and cleaning hard, if not impossible and could be detrimental to your car's finish. Next thoroughly wet down the car. This will remove dirt and road debris which will cause scratches if you skip this step and start using a sponge and soap on the car. If it is a hot day, be sure to routinely wet the car so it does not dry suds or cleaning chemicals on it.
Next use a car wash solution, don't use general purpose detergents and cleaners that were never meant for car care and car washing. A car wash solution will not dry out your paint or strip and possibly remove protective coatings. A long armed, soft bristled wash brush will greatly reduce the time it takes to thoroughly clean your car. It will also make it easier on your back and muscles. A good quality brush can be cheaply obtained at Walmart for about $10-$15 - buy one, you will be glad you did. When you have finished washing the whole car, use a chamois to dry off your car. A chamois will remove water quickly and not leave lint which terry cloths are prone to do. Routinely washing your car will remove things like bird droppings, bugs and industrial fallout which are all detrimental to your car's paint and finish. If there is road tar or stubborn bugs left after washing you should use a bug and tar remover prior to waxing and polishing.