As I have done a lot of Detailing over the last year I thought it might be interesting to some to share some simple tips on washing.
Rinse car down, pressure washer and foam lance are nice tools
1. Use two buckets. One with the Soapy solution and other one with Water to rinse the wash mitt
2. Do not use a sponge but a wash mitt and plenty of soapy solution
3. Do one panel at a time, Soap in with mitt and than rinse it clean in the water (rinse) bucket. Never put dirty mitt in soapy bucket
4. If you drop the mitt than take another one
5. Rinse down with plenty of water, if you are in conditions that the soaping dries out quickly than rinse panel at a time during soaping
6. If possible use soft (low on minerals) water, at least make sure the water does not dry on the finish but is dried with cloth
7. for drying use microfibre cloth of good quality (there are poor ones out there!), e.g. Chemical Guys, Zino, poor boys etc.
Keep a good sealant or Wax on the car e.g Swisswax, Dodo
Check out detailing forums esp. the instructions sections. Or ask

Nice source:
http://www.detailingworld.co.uk/forum/showthread.php?t=4637