Education is the key.  
Think about attending  workshops. 

Many experienced cemetery preservationists understand that someone with little or no experience in this field of work can do more harm than good. Even a well funded project without the proper planning can do irreversible damage to the historical integrity of the burial ground. 

While the person that is untrained may have the best of intentions and you do not want to discourage them in their efforts, more often than not they can cause additional damage and problems that need to be addressed. Saving Graves highly recommends that you attempt to schedule at least one training workshop for your volunteers prior to starting the project.

Training workshops for volunteers can help keep costs down and as much work in-house as possible. Workshops (or one extended workshop) can train volunteers in skills necessary for such tasks as mapping, documentation, surveying, photographing markers, site maintenance, stone resetting, and stone cleaning.   A training workshop gives individuals the opportunity to gain experience in identifying problems they may encounter and hands on experience in arriving at correct solutions. 

Sometimes the most valuable lesson is a clear understanding of what is best left to experienced professionals. There are many experienced professionals that are willing to meet with your group and provide training or pass along their knowledge and expertise in the cemetery preservation and restoration fields.

A Graveyard Preservation Primer  by Lynette Strangstad  "Written for non-professional and professional preservationists involved in small to mid-size graveyard preservation projects, this basic primer explains in step-by-step fashion how to preserve and restore a graveyard. After reading the suggestions outlined in this book, you will be able to plan a well organized preservation project. In this way the common mistakes and waste of resources that characterize many well-intentioned graveyard preservation efforts can be avoided.  Restoration is discussed with recommendations as to what lay people should and should not undertake."  144 pages with index and illustrations.  Order from Association Gravestone Studies website.