Polishing is usually a step before waxing.
I try to do a thorough detailing once (or twice) a year, where I use a cleaner, then a polish, then a wax.
After that point, if you're using a good car shampoo (like Meguiar's), it should clean off everything that's on the surface, except the wax. Then you just need to quick detail it and it should be as good as new.
If you're washing and quick detailing it on a regular basis, you probably can go 2 or three months (depending on your climate and how picky you are about your cars appearance) between waxing.
My $.02, hope it helps.
