I second the clay bar recommendation.
I use Duragloss Total Performance Polish (#105)
www.duragloss.com
Best when used with the Buffing and Polishing cleaner (#652) to clean the paint and Polish Bonding Agent (#601) to help it set.
Maintain it monthly with some Duragloss Aquawax spray detailer (#951) and one coat of polish has lasted the better part of a year with the car outside.
Lots of good detailing info at
www.autopia.org/forum/