IMHO----Wash with Dawn liquid soap. Dry, then clay bar. The clay bar will remove all the crap that is on the paint. Wash again, with a good car wash soap(Meguires) makes a good one. Polish with a good sealant(Wolfgang 3.0) The reason you put a sealant on first is because the sealant lasts for about 6 months+. Top the sealant with a good wax(Collinite 845). This wax is one of the best kept secrets around. Does an excellant job and last about 2-3 months. Most all waxes only last about 60-90 days before you have to put another coat on. All these products can be bought from autogeek.net. They also sell other professional detailer products and they explain the products uses, how to use the product and what you can expect. They also do product comparisons. If nothing else it is a great souce of information about detailing and how to treat your paint properly. The first time takes the longest, after that just use a detailer spray after you wash and dry your vehicle.
Jay