Do:

Read the directions on the car care products you use. Some might have special tips about how to achieve the best results with that company's products. Others might have a specific time that they want you to wait before rinsing, or buffing, in the case of leather creams and car waxes.

Don't:

Just use any old cleaner on your precious car's paint (or on the seats). Baby shampoo is safe enough for babies, but other cleaners might not be. This is one area where Lysol can't help, and dishwashing liquid is terrible for car paint. Use some actual car cleaning products for a good result.