I was playing against a friend that played with a deck with redirect in it.
There were several times where we couldn't agree on how redirect works.
One example is he tried to redirect a diabolic tutor. I argued that since diabolic tutor doesn't target anything, he couldn't change the spell. He argued that he could choose himself for the spell and the "you" in the card text would refer to him.
Another example is when I played an oblivion ring. He argued he could choose a new permanent to exile. I argued that it was a permanent with a ETB ability and so it couldn't be redirected.
Could you explain how redirect works?