I just use car wash soap like Turtle wax or Mequires in a bucket of water with a sponge, and the wax keeps beading for many months. But I'm sure others have more sophisticated suggestions.
I use Mothers California Gold exclusively now. In the past I have also had success with Meguiars Gold Class shampoo and even Blue Coral. Pretty much any car wash product actually designed for washing cars should work for preserving the wax. Stay away from degreasers like dish washing liquids, etc.
Meguiar's Gold Class Car Wash will work along with any major car wash soap as long as you follow the directions and not have too high of a soap concentration.
Any name brand car wash will do what you want. Even more important is the wash media....sponges are a total no-no (except a grout sponge) as are rags from the garage. Get a quality wash mitt and microfiber drying towels. Also google the two bucket method for washing a car.
Most if not all specific car wash soaps should not strip the wax. And many will enhance the finsih with MFG specific ingredience(poor spelling).
Just don't use household cleaning products such as dish soap. It's good for cleaning and removing dirt and grease/oils but, will stirp the wax slowly over time instead of enhancing the finish.
People have their favorites such as soaps that are:
*Easy to rinse
*Leave no/less water spots
*Suds Heavily
*Suds Less
*Enhance the paint finish(usually using a silicone)
*Smells Really Good!(these attract too many BeeZ while I'm washing the car. I've been stung too often)