I've found that if you want a long lasting protection get some sort of Paint Sealer. I used jetseal 109 on my whirte Focus ST and found it lasted about 6 months if I washed it with the right stuff. I now have a white Kuga and plan to do the same as soon as I can get the thing clayed.
There are a few good car detaling sites out there or look up a local car detailer and have them do it first time for you.
Certain LSP's (Last Stage Products) can look better on some colours; whites and silvers can look better with a sealant, whereas, darker colours tend to look better with a wax BUT you can also mix the two, there is no right or wrong