I know I've posted this before at some point, but I told Therese I'd post it so that she could see what I was talking about. Here is an online version in parallel German and English.
All flame and internet-argument guides pale in comparison to Schopenhauer's work on how to win an argument per fas et nefas.
Learn how to annoy your friends and vex your enemies using tricks such as "Defense Through Subtle Distinction," "Putting His Thesis Into Some Odious Category," and "Bewildering Your Opponent By Mere Bombast."
Seriously, though, even if you don't want to sink to any of these, it's a good read because it gives you a good idea of what arguing is likely to be like in real life rather than in the idealized circumstances you hope for.
It is perhaps not useful within the context of any given debate but certainly an interesting exercise when reading articles or disputes on the internet to recognize instances of the tactics Schopenhauer lists and mentally categorize them. For instance, here's an example of a combination of Stratagem #1, exaggerate your opponent's argument beyond its natural limits, and #13, make your opponent choose between a proposition and counter-proposition both of your choosing.