To give Geocoding API the best opportunity to find a precise match, it is helpful to format your addresses as close as possible to the local postal standards (e.g. put commas between components, use standard abbreviations, etc.). Additional tips for formatting can be found in the FAQs.
If possible, it could be helpful to break your addresses into their individual components and pass them to the "components" parameter instead of the "address" parameter (more on that option here: https://developers.google.com/maps/documentation/geocoding/overview#geocoding-lookup). Even if you can't do it with the whole address, specifying a country or postal code component (if you're confident they are correct) will restrict Geocoding API to only looking in those regions, and so may make it easier to discern good matches from bad (more on component filtering here: https://developers.google.com/maps/documentation/geocoding/overview#component-filtering).