What is the correct way to create a term store for taxonomy planning for a medium size company?
Is it import from excel file or creation through website?
Again this is for a medium size company?
I would use excel (use Wictors Excel Sheet: http://www.wictorwilen.se/Post/Create-SharePoint-2010-Managed-Metadata-with-Excel-2010.aspx) or Powershell.
With that approach you can implement the taxonomy on Dev/Prod - with the same values.
With Powershell you can even have the same Term Ids.