1) Don't wash your car in the sun.
2) Don't wash your car in the sun.
3) Go from mild to abrasive; try just using a high-quality wax first. If that doesn't work, try a clay bar. Then, on to a mild polishing compound, maybe Meguiar's #7, then you'll start into the cutting stuff.
If you've never done it before, stop at the clay bar, take it to a detailer, and watch them work. They may spin you a line about the super-special products they are using, but a LOT of it is technique and knowledge of the proper products for your requirements. Check out Meguiar's homepage; this is not to say you should use only Meguiar's, but I've had good luck with their products (although I do only have one Best in Class from a Super Chevy Show! :rolleyes:)
Don't wash your car in the sun.
I use the Mr. Clean car wash gizmo, primarily for the filtered water rinse - works pretty well at getting the harder water off and significantly reducing any spotting that may occur from water deposits.
Just my $0.02.