Flossing and brushing like everyone said, but toothpaste matters I used to swear by the Sensidine with “Novamin” (Calcium sodium phosphosilicate), from what I understand it can actually repair minor damage (e.g. prevent a soft spot from becoming a cavity). Sadly last I checked there was some patient in the US preventing it from being sold here. I brought back a decent bit when I moved back from the UK, but its all gone now. Amazon.co.uk or Boots.co.uk may ship it (but then it becomes legally questionable, I don’t know how close stuff like that is watched for at customs).