Be generous. Assume the best first. Don't assign evil motives to other parties. They may have intended something else. Let the principles of love guide our discussions (I Cor 13:4-8).
Be respectful. Don't begin a response by insulting and insinuating that the other parties are intellectually deficient. Just address the issue without resorting to ad hominem attacks. Kindness and respectfulness should mark all conversations.
Be willing. It's possible that we misunderstood something. Be willing to discuss and foster good communication through definition and clarification.
Be open. It's possible that we are wrong ourselves and haven't thought something through. Consider the other position and make sure that we understand it before rejecting it outright. If we are still sure that we disagree, then proceed with the other principles still in mind.
Be direct. Being generous and kind does not mean that we have to beat around the bush when we address the issue. State clearly the objection and the reasons for the disagreement.
Be honorable. We all make honest mistakes in our reasoning and conclusions, but if we purposefully twist or distort something in order to win an argument, we have crossed over into dishonesty. This is never honorable or right.
Be committed. First, be committed to the Lord and His truth. Then be committed to the well-being of others. Winning an argument is pointless just for its own sake.
Be logical. It is one matter to just state, "I disagree," or to just state a contrary proposition. It is another matter to state the disagreement along with reasons. Learn how to make actual arguments. If we want others to consider our positions, we need to able to give the "because" for our positions. If we can't state the "because," then we don't have adequate grounds for actual discussion.