Keeping a car tidy, serviced and damage free will only increase the resale value. A car's paint job is often overlooked when reselling but it is crucial to the integrity of the vehicle. Of course there are the obvious ways to scratch up a car's paint, including dings in the parking lot, driving on gravel roads missing the key hole over and over, but it is the less obvious sources that can ruin your paint job without you even knowing it.
One source that is detrimental to a car's paint job is bugs that splatter on your car while driving. Just washing your windshield is not enough. The insides of bugs are acidic and can slowly damage your paint, especially if you leave them. It is encouraged to get a good car wash solution and remove the remains as soon as possible.
Water sprinklers are also a problem for paint that often go overlooked. Minerals left behind from the water bond to a car's paint, causing hard to remove water spots all over your vehicle. It is best to try and avoid leaving your car near them but if that is not possible then take your car to a repair shop to have them removed.
Dirt in your car cleaning tools and additional products can also damage a car's paint. This source of paint damage is especially frustrating because there you are just trying to get your car looking nice and spiffy, when you realize at the end that you caused more harm than good. Dropping a microfiber sponge on the ground can cause it to pick up dirt that will scratch your car upon scrubbing, so watch out when washing.
Watch out for tree sap. Tree sap is especially damaging to a car's paint, especially when you consider past cultures used it as an adhesive. Make sure you don't just wipe the sap and assume the problem is solved. Tree sap can leave a residue behind that will dry out and damage paint. Use a bug and tar remover to remove dried sap and a clay bar treatment should take care of the remaining residue.
If you spill coffee or soda on your car make sure to wash it off immediately. Both are acidic, like bug guts, and will ruin a car's paint job. It is important to not let them sit because the corrosive chemicals will break the paint down. Wipe it off and get to a car wash.