Let me start off by saying if you do not have a decent amount of time (this usually takes me about 2 hours or more) you should probably just do what the rest of your peers do and take your car to a commercial washer.
Now, if you actually care about your car, or want it to look pristine, you'll follow the steps I'm about to explain below.
The first step of any "how to" is to locate all of the materials needed for the procedure. You're going to want to purchase the following:
Microfiber wash mitt Turtle Wax TW45201 ICE 3-in-1 Microfiber MAX Wash Mitt
Drying towel Turtle Wax TW45200 ICE Microfiber MAX Drying Towel
Now for the optional, and most time consuming, products:
Clay bar (I prefer liquid because it's much faster) Turtle Wax T466 ICE Liquid Clay Bar - 16 oz.
Wheel/Tire Cleaner Mothers 05924 Foaming All Wheel & Tire Cleaner - 24 Fl.oz
Microfiber Towels(you may need more than 2) Turtle Wax TW45203 ICE Microfiber MAX Detailing Cloth - Pack of 2
(These are the products I use, you're not limited to them, but this is what I've found works best)
Now that you've allotted all of your items we'll get into the steps...
1. Pull your car into a shady area (Or garage with a drain if possible)
2. Rinse your car off REALLY well, get all loose dirt completely off
3. Get your two buckets mentioned earlier and pour about a three inch diameter circle of soap in the bottom of one.
4. Fill both with water (you should have one with soap and one with just water)
5. Get your wash mitt and dip it in the soapy bucket (squeezing it tight before dipping to maximize withdraw)
6. Begin scrubbing the car with the mitt, but the trick is GO WITH THE WAY THE AIR HITS THE CAR.
7. You should be going in a back and forth motion with the aerodynamics of the car (this avoids swirl marks) then RINSE occasionally in the all water bucket by squeezing tight inside the all water and repeating step 5.
8. Do steps 6 and 7 to the entire car and make sure all dirt, road grime, bugs, etc. are completely off of car.
9. Use the wheel/tire cleaner at this point and Rinse car thoroughly to remove ALL soap suds.
NOW EITHER DRY THE CAR OFF AND STOP OR PREPARE FOR WHAT MAKES THE CAR PRISTINE.
10. Get your liquid clay (or regular clay if you prefer it) and follow the directions on the label.
11. Once you've clayed your entire vehicle (rinse it off THROUGHLY if it's liquid clay scrubbing all areas with your hand while spraying water)
12. Dry the car off well and make the strokes in the direction the airflow goes when driving.
13. Get your microfiber towels and wax ready.
14. If you bought the aforementioned kit of liquid wax it will have an applicator that you will use to apply the wax.
15. Rub the wax into the car in small sections going with the airflow again to avoid swirl marks.
16. Let each section dry to a haze (as mentioned on the product's label) and wipe off WELL with microfiber cloth(s)
17. Once you've waxed the entire car make sure to go back over one last time checking for wax, it will harm your paint SEVERELY if left on in the sun/heat.
18. You're finally done. Take pictures of your new shine and take it for a well deserved drive!
I may put up an interior cleaning howto next. This is how I wash my cars and I get tons of compliments on how they look all the time. You'll be amazed at the results, especially if you have an older car. This didn't take as long to write as I expected it to...