Put your hand in a plastic bag then run your hand over your car's paint. If you feel it is rough, go ahead and buy a good piece of clay. For results that will leave your paint feeling like glass, first wash your car from the top downwith dish soap and a terry cloth mittto remove any old wax, grease, etc.Once finished, dry with either a chamios or microfiber towel. Again, for best results, spray the car down with body shop prep and wipe. Once that has dried, go ahead and work in small sections with the clay bar. Spray a LIGHT mist of clay bar lubricant over 1 body pannel at a time. Run a quarter sized piece of clay over the lubricated area making sure to cover the whole area. Once complete, go ahead and wipe it dry again. After this process is done to the whole car, go ahead and apply your favorite wax to seal everything. I personally recomend Meguiar's Gold Class wax or Zymol.

What it does:
Body shop prep will take off all surface debris and old wax that still lingered.
Clay bar takes all the industrial fall out and pollution out of the pores of the paint.
Wax will seal the pores so you don't get all that junk back in.

What you need:
Dawn Dish Soap
Wash Mit
Microfiber towels
Body Shop Prep
Clay bar lube
Clay bar
Wax
Wax applicator

http://www.detailyourcar.com
I recomend using the grey or light blue clay bar and their lube to go with it.

 

Did this before on my Corvette. Works great!

 

Claying a vehicle should be done quarterly. Or before doing any correction process or even just before apply any wax or sealant.