What is the best way to keep exterior clean without damaging finish?

Wash it regularly with soap and water and polish it at the end.

You do not really need to use any other chemicals, they're just a waste.

Like the first guy said, a simple wash & then a wax. As far as car washes out there, there is so many. Stay away from the really cheap ones, they r exactly that, cheap. They do not offer u much cleanliness & r not that good for ur paint. l would recommend turtle wax ICE car wash, try it out & see if u like it. ( l believe its about $9 a gallon at Costco). l use it on all my cars because it works wonderfully & does not leave behind any residues or anything. Once a month after washing ur car look into waxing it, l use Meguairs cleaner wax (About $7) & the car shines so nicely. The wax does a good job at repelling contaminants & water as well, which is great since it looks cleaner for longer amounts of time.

Wash with Car Shampoo.You wont need to polish the exterior.