There are lots of articles on how to wash a car with varying levels of knowledge behind them.
Most miss a very important aspect to a high quality car wash...using 2 buckets. The "2 bucket method" greatly reduces the chances of introducing scratches into your paint. It's a simple and inexpensive addition to your car wash that will help you safely keep your paint looking great. This is the same process we use when getting cars ready to detail.
The car wash process:
First Step: fill 1 bucket with clean water, this will be the rinse bucket. For under $10 I would strongly recommend investing in a Grit Guard, this is a plastic screen that sits at the bottom of the bucket. The Grit Guard prevents dirt from swirling back up in the bucket and re-attaching to your wash Mit.
Second Step: Fill the second bucket with an inch of water. Add some car wash soap from a reputable company. Spend a couple of extra dollars on a quality soap from a boutique level company, it will last a long time. Never use dish soap as it can remove wax from the surface of the paint. Fill the bucket to the top using a jet stream setting on your hose nozzle generating lots of foam.
Contrary to popular belief it is best to start with the wheels first, then empty both buckets, refill and then do the body. It is also important to have tools specific to do the wheels as to not transfer contaminants to the paint. A California Wheel Brush, a small micro fibre wash sponge, a stiff bristle tire brush and a soft paint brush for around the lug nuts is a great start for a wheel wash kit. Use the wheel brush to clean behind the spokes and around the inside barrel of the wheel, a huge time saver.
After the wheels are clean empty and rinse out the buckets. Refill with water and soap as explained above. Starting from the roof down wash 1 panel at a time then rinse. For the bottom 6 inches or so use a different mitt designated for this task. Make sure you don't apply excessive pressure and "scrub" the car, gently draw the mitt across the paint with little pressure. Try to wipe the mitt over each section only once, overlapping your strokes by 50%.
Remove the nozzle from the hose and starting again at the roof rinse the car off with a gentle stream of water. Using the proper technique you can cause water to run off the car reducing your dry time.
If you have an air compressor you can use it to blow out the cracks and crevices, your compressor should have a filter on it to prevent blowing contaminants on to the car. Blowing out the nooks and cranny's prevents drips from appearing later. An even better solution is a blower made specifically for this task, a popular one is the Master Blaster from Metro Vac or one of their smaller units if it doesn't fit your budget. Given the high volume of air these produce you can actually dry the entire car eliminating the need to touch the paint surface, not to mention speed up the process.
If you don't have a blower you should buy a waffle weave microfiber towel made specifically for drying vehicles. The technique I use is to lay the towel flat on the paint and gently pat it to absorb the water instead of wiping the car with it. Elimination of movement on the surface reduces the risk of scratching the paint.
Finally use a good quality tire dressing to make the tires look new again. Use a low gloss product and apply it to a cloth or applicator, do not spray it on the tire. Let it sit for a minute then wipe the tire again with a dry rag to remove excess dressing, this step will prevent it from getting on the paint when the tire starts spinning.
Check my other articles about car detailing to learn processes to help keep your car looking like new.
2 - 5 gallon pails
1 - Grit Gaurd
2 - good quality wash mitts
1 - wheel brush
1 - small micro fiber sponge
1 - soft paint brush or similar for wheels
1 - high quality car wash soap
1 - water hose and adjustable nozzle (with quick disconnect is handy)
1 - waffle weave drying towel
Blower made for drying cars