Begin with documentation: photograph and catalog existing wallcoverings, plaster condition, and any visible moisture issues before any work begins. This record protects both the homeowner and the preservation history of the property.
Commission a moisture and substrate analysis before selecting any wallcovering — this single step prevents the majority of installation failures we're called in to repair.
Confirm whether the property carries National Register status or falls under local Board of Architectural Review jurisdiction, as this may affect which materials and methods are permissible.
Finally, budget for surface preparation as its own line item, separate from material and installation costs — in historic homes, it is frequently the largest expense in the project.