For convincing people in person, I've always tried to follow the maxim "Don't argue, discuss." You can present arguments, but it's important to frame them as "I think X because..." or "My take on this is X" and so forth, rather than "X is wrong because..." or "The usual solution to this is X, but that doesn't make sense because..."

With online debates, it's different because your actual interlocutor is only a small part of the audience to your arguments.