How do you actually demonstrate confidence?

In other words, how do you become more on a "bad boy?"

Every now and again, I (28m) come across guys who walk with a cocky attitude, the type of guys who aren't afraid of confrontation and most likely ignore rules that are realistically silly.

Whenever they speak, people often listen because they sound like they're about to say something interesting, even if it's stupid.

I have no idea about America, but in the UK we use the slang term "chav". You can say what you like about "chavs" (I personally don't like them), but one you thing you can't argue with is that (some) women like the whole bad boy persona, and these guys have perfected it.

I obviously don't want to change my entire personality, but I do want to become slightly more of a bad boy.

At 28, would it even be possible, or are those guys the way they are due to their upbringing?

Thanks.