Erosion and discolouration are the greatest and most frequent hazard to memorials. Such two things are unavoidable to a certain extent. The wind and the rain can not stop changing the region and the stone itself around a grave. There are, however, several ways to reduce the influence of these effects. Discoloration is the simplest to eliminate as it essentially eliminates material from the tomb that can stain the stone. Seek not to place the headstone below something that can drop or spill it, so let the trees and the edges of buildings go away. Over time there would be a stone marked by a leaf not removed or a steady drop from an old gutter. It is also necessary to check and clear the stones periodically, as even those who are not below it may well gather leaves at any time of year in autumn or bird droppings. Unfortunately, sun bleaching the color out of the stone is inevitable.
Erosion can also be minimized by seeking a more sheltered location, but it may prove difficult to do so without being under a tree or a building at the same time. Fortunately, damage to erosion can be repaired. A gravestone may be restored to its former splendor by removing a very small layer of the stone surface and recutting the designs and letters.
The other big threat, which is fortunately rare, is that of vandalism or demolition of the cemetery by the local authorities if they think that the grave is dangerous. You will prevent vandalism by selecting a cemetery that has a decent reputation to look after the existing headstones and keeping up to date with any news about nearby vandalism. The same approach is used to discourage officials from destroying graves as maintaining contact with cemetery owners helps you to alert you of any changes and to seek and negotiate a more favorable situation.