This is a brief note to point out a few great articles by Tim Keller on theological engagement.
The first one is entitled Gospel Polemics.
The second one gives Three Rules for Polemics.
And the last one gives some very good guidelines from the the 17th century Scottish divine George Gillespie on how to Be Winsome and Persuasive .
I find all that I read very useful for any kind (not only theological) of debates and discussions.