Tools can be very useful, but unfortunately they cost a lot of money too:
5 tube sites - OSE
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I would say that majestic.com (good site, especially at these prices, as compared to the other ones), could be continuously, and SemRush.com (Guru Plan, expensive), monthly, if needed, would be something that I would need for sure.
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This is not a tool, but it is an important thing, that can be added here too:
Advanced search operators, Google