One of the most oft referenced pieces of magic writing, this article formed the foundation for understanding of role assignment for many players when it was first published on The Dojo. While the examples used may be a little tough to understand for newer players, the lessons it teaches are timeless.
Beating Thoughtseize And Other Discard Spells – by Ross Mirriam (Paywall)
Mirriam talks about fighting discard spells such as Thoughtseize, giving different advice for midrange, aggro, and unfair decks. While he avoids giving too many examples, all of the information is clear and well explained.