I use 2 methods that work great!
1- This used to be my favorite method- "The 2 bucket Method"
Using 2 buckets, one for "the suds" and one for "the rinse".
Wet the entire vehicle washing away anything that can be removed with water pressure.
Wash one section at a time, using a Microfiber Wash Mitt, as they are great for cleaning and you use less pressure on the finish, decreasing the chance of adding any marring to the finish since the Microfiber is doing the cleaning and you do not have to "scrub".
After washing each section(always working from the top down and keeping the car wet), rinse the mitt in the rinse bucket, as this will kep your washing solution clean and free from debris. (remember to keep the vehicle wet as you are washing)
When you are finished washing the vehicle, switch to wash mitt #2 (you NEVER want to use the same wash mitt for your tires/wheels as you use on your paint, as brake particles and road grime can and will get embedded and can cause swirls to your finish).
2- This is my favorite method-
Using only one bucket with car wash shampoo, use the same method as above, except when it comes time to rinse the mitt, use the spray jet to "pressure wash" the wash mitt clean. It is faster and less "bending and stooping" :)