Dig up each piece of the gravestone if it is a flat marker. Flat marker pieces may have shifted deep into the ground over time due to varying conditions. For stand-up markers, there is no digging. You will work with the burial stone in place. Cemetery personnel usually place the broken pieces of a stand-up marker next to it so they are easy to locate.
Wipe the stones using the soft terry cloth and mild dish soap. It is important to not use abrasive sponges or harsh cleansers, as they will damage the natural texture of the stone. Using harsh chemicals may also result in corroding the stone and removing the carving.
Rinse all cleaning residue from the stone using only water on low pressure. Leaving any form of chemical agent on the stone will cause the cement to not adhere the way it needs to, and it may deteriorate the stone.
Apply cement between the cracks of the stone. This is the most important step. If you are repairing a flat stone, it will be necessary to complete this step on a flat surface. If you are repairing a stand-up stone, then you will need to set up some sort of barrier such as a pallet wall to hold the top of the stone in place while the cement dries.
Line up the broken pieces of stone along the appropriate edges with the cement in between as an adhesive. Before the cement dries, you want to scrape or wipe off any excess cement that overflows from the cracks. This will ensure that the stone maintains a quality look.
Level the ground using a shovel to replace the flat marker.
Replace the flat marker once the cement has dried. Remove the support system from the stand-up marker once that cement has dried.