I have only realised a few days ago that insult swordfights are not a thing of the past. In fact, it's actually used a million times on a daily basis.
Yes, it's our beloved internet memes. The similarities are so high, it's actually ridiculous.
First of all, you need to learn "insults" first. You do this by interacting with different "people". If you have talked to many "people", you will have a wide variety of "insults" to use. But, you can't just use any "insult" - it has to fit. You need a proper "response", otherwise, the "insult", used out of context, is just a big fail.
Isn't that amazing?