main thing to make sue you keep to a minium on the candy white is tar marks flicked up from the road, you can remove this with a clay bar and clay lube, you can buy the megs clay and lube pack for a tenner.
next use a decent wax so something like dodo diamond white which has no coloured pigment in for use on light coloured cars would be great a couple of coats after a good wash just puts a nice barrier on stop things like tar sticking to your paint work as much.
hope that helps