Mostly self taught, but influenced from a variety of sources. I'm a center-left, liberal minority who has been serving a career in a right, conservative establishment for over a decade. Debate is unavoidable! After so many years, I've gotten pretty good at it. The reason I'm so good at debating things/issues/people, is because I cover my tracks to ensure that I will always win the debate (if that is my intention) or if I'm playing devil's advocate, that the other person gains more information on a topic when they leave the discussion than they came into it with. I do that in several ways:
1) I never "debate" a topic that I am ignorant about. If I don't know shit about car engines, I'm not going to attempt to debate someone who might actually know what the hell they are talking about because I'll look/sound like an idiot.
2) I do research. I'll generally study the key elements in the debate by looking up the facts, stats and histories of whatever it is I'm debating. That way, when someone tries to throw out something that is incorrect, I can cite the correct information and point it out to them. Doing so always weakens their argument and strengthens mine.
3) I examine my own debate points for weaknesses and try to break down the flaws in my logic BEFORE I actually bring it up in the debate. That way, I make it more difficult for my opponent to find any actual flaws in my logic that I'm not capable of explaining away.
4) I don't get emotional. A lot of people cannot debate a point without becomming emotional about the topic. I can debate passionately, without letting that passion blind me into losing focus on the facts. A debate can only be one using logic and reason. The more emotional your argument is, the weaker it becomes.
5) I can easily spot a strawman argument. A lot of times, people realize that they can't answer/refute/respond to a particular point that you bring up, so they try to turn it around on you or change the direction of the debate by completely ignoring that fact altoghether. In this way, they can make it seem like they are actually winning (if you take the bait and play along).
6) I can agree to disagree. Once all the facts are exhausted, there comes a point where a particular position in a debate merely become opinionated. I believe that everyone is entitled to their opinion and that as long as you make an attempt to justify that opinion using facts, it is no longer a win/lose debate. Some debates are stalemates because of this, yet people often refuse to accept a debate ending in a stalemate. They MUST win and they MUST get the last word regardless. I'm perfectly content to let them do that!
7) I'm not afraid to admit that I didn't know something, or that I am wrong. Sometimes, people realize after 30 minutes of debating an issue that they are wrong about something and that the entire basis for their debate was from an incorrect assumption. But instead of admitting that and backing off or changing their position, they continue to argue as though they are STILL correct! Why? Because they are afraid to lose and don't like to be wrong. People like that, I generally tend to avoid!