Determining a likely date of construction for an old house usually requires both documentary and architectural research. Documentary research that you can do yourself includes reviewing deed and probate information, tax records, and local histories. Your local historical society may also have other pertinent information as well as historic photographs.
Documentary research can be quite conclusive, but in some cases physical investigation will be necessary to supplement and/or corroborate the documentary evidence. The investigation of the architectural fabric may require a more trained eye and some technical assistance from a preservation professional.