1. Most arguments come down to defining words, even if you may not realise it.
2. Don't follow rabbitholes. Don't deviate from arguing your core premise.
3. You're not trying to prove the other person wrong, you're trying to find the truth.
On #1 for example; I watched a video of a conservative arguing liberals (or something) about a few premises, including "gay marriage does not exist". It was immediately clear to me, but apparently not to the people in the video, that this guy has a different definition of "marriage" to me. That's the breadth of the disagreement. That's all people should've argued with him about. But not one person did. Even when he described his definition of marriage, and how his premise comes about from that definition, everybody immediately became sidetracked. There's just no chance of finding common ground behaving like that.