Have the home inspected so you'll know if there are structural issues or problems with wiring and plumbing before you make changes.
Remove additions to the home. Return the structure to its original configuration by removing porches, awnings, shutters and other additions that aren't appropriate.
Paint the exterior a color that's true to your home's era. Repair and repaint porch railings. Replace railings that are damaged or of a different style than the original. Have the roof replaced to match the home's original.
Remove and replace interior moldings and other details that have been added. If original doorways or windows have been covered, remove the covering and restore the doors and windows to their original state.
Research the color schemes typically used in homes of the era and repaint the interior. Add textures or wallpaper where appropriate.
Restore the floors. If they can't be restored to their original state, replace them with matching materials. Try to find re-purposed wood--it's sustainable and doesn't require energy for manufacturing.
Replace hardware with originals. Advertise in preservation magazines, watch online auctions and travel to salvage yards and country auctions to find replacements.
Preserve the windows. Make repairs and cover them with storm windows. If the windows are in good shape, they don't need to be replaced by modern windows.