Hey @TVaz,
There are a couple of things you can do. First, during the important you should catch any duplicates by email address. Additionally, check the validation on any customer or employee facing forms to ensure that the data is going in formatted correctly and cleanly. That should take care of a good amount of the duplicates, but if you want to go to the next level you can use Ops Hub or the API to custom code something that will be able to check using other fields.
Also wanted to mention that Insycle (full disclosure, I work for Insycle) allows you to identify duplicates using any field in your database. So you could catch duplicates using fields like addresses, phone numbers, names, etc. And that goes not just for contacts, but companies, deals, tickets, and custom objects as well. Additionally, you can set up advanced rules for retaining data during the merge. That way you can ensure that you never lose data when merging, as HubSpot typically keeps data from the most recently updated record/field.