I also clone elements that I deem unnecessary or not aesthetically pleasing. These elements are rarely “trash” (empty cans and other litter as I can easily remove these prior to taking the photographs. Rather these elements are either natural features that I can modify in the original scene or elements that I did not “see” when I took the original captures. These for example include branches or twigs intruding into the borders of the image, patterns on textures that are incomplete or visually unsatisfying and any other unwanted elements. 
So whether I do minor cloning, burning or dodging or erase a twig that impacts upon the aesthetic value of the image it always must be believable and a representation of the actual scene. For instance a twig could have been broken off to clear the frame of the capture for this reason but I would rather remove it post capture digitally than intruding on nature. A branch or flower that has been covered in shade in the capture could for instance be slightly lit up to bring out the actual colour of the flower. So the true colour in natural light is still represented. Basically like the eye sees it.
With my Artography styled photographs I once again do not alter the actual scene in any way besides radically changing the frequency of light reflected off the subject, visual to the viewer. (Bending the angle of light visible to the human eye or changing the spectrum). No colour is added by filtering or otherwise.