Always wash and wax your car in the shade.
Make sure the first thing you do when you get the car is apply a high quality wax such as Maguire’s Gold Class or Zymol after the car has been fully washed and dried. Make sure to get a nice full even coat on there.
You don’t need to wash the car every time it's dirty. The dirt will not "scratch" the paint unless you rub it in.
The key is lots and lots of water when you wash.
Drench the car and the high quality washing cloth that you buy from the auto parts store. No sponges or tee-shirts please.
I like the Maguire’s "soft wash" I think it’s called. It is pink and in a clear bottle. Use a cap full or two and make sure that your wash cloth is clean and soaking wet before you use it. Wash out the pail that you use every time you wash the car. I like using one of the Igloo coolers with the top removed. It has a nice handle and carries a good amount of water. Wash the car from the top down washing the canopy area first and then rinsing it off so that the soap water/dirty water does not dry on the finish. Move to different sections of the car and wash and rinse them individually like say the front clip.
Wash off soapy water then move to the next section.
After the whole car is washed use an absorber material to clean up the residual water that has not beaded off your nice wax job.
I REALLY like this thing called "The Absorber". It costs ten bucks but has been the best drying tool I have ever used. Find it at "Pep Boys", etc.
Open all the doors and dry inside the door jambs. Get all that water out as it will just pour out after you start driving and adhere dirt to your freshly washed car.
So to Sum up:
1)Good thick quality wax to protect your finish.
2)Lots of water
3)Soft clean quality washing cloth.
4)Clean bucket with fresh water.
5)Good quality washing soap. Please no Palmolive like this one girl next to me at the manual car wash. :x
7)No automatic car washes. Some will say that the touch less are OK but its your paint so do as you will.
8)Quality drying material that is also washed regularly.
I have had three black cars and one dark green one and have not experienced swirl marks that could not be removed by buffing and waxing again. Allot of the swirls you may see can be in the wax and possibly in the clear coat but can be removed.
Black kicks ass.