On TVs and Movies, I
alwayshear thenative speakers say "Guess what?" and "You know what?" I want to know the meaning of them and how to use them properly?
They both signify that the speaker has something interesting or important to say to the hearer. They mean the same thing. It's a way of building up suspense in the hearer.
The common answer to both these phrases is, "What?" - meaning "No I don't know what, and I don't want to guess. Just tell me."
Sometimes, after the speaker says "Guess what?", the hearer will play along and try to guess what the news is.
A: Guess what?
B: Umm ... your cat died?
A: No, I've been accepted into Harvard!
On the other hand
You only use this phrase when you are about to contrast what you've said with what you are about to say.
Also, recently I watched the popular American TV series called "Breaking Bad", and I found that they almost only used "You know what?" in the conversation, they never use "Guess what?", I want to know if "You know what?" is more popular than "Guess what?"? Is "Guess what?" outdated? Please advise.
No, they are the same. Different groups of friends fall into different speech habits. You can't read anything into that.