Punching the phrase into Google and summarising the hits, I come up with "If you believe in the position that the speaker's coming from, you'll believe where they're taking you to."
In comedy, it means that if the audience grins when you're setting up the joke, they'll laugh when it pays off.
If a salesperson tells you "You need a new car because your old one's busted," and that's exactly how you feel about it yourself, you're more likely to buy from that salesperson even though they didn't tell you anything you didn't already know.
In politics, if someone stands up and says "Problem X needs fixing!", and you think "Yeah, it does!", you'll be likely to at least listen to that speaker's ideas for fixing it - and maybe support the idea or vote for that person.
On the internet, if there's a meme going around about, for example, vampire bunnies, called "Vampire Bunny meme!", and you think vampire bunnies are cool, you'll probably read the meme and maybe fill it out.
In publishing, if the first chapter (or page, or line) of a book, or its back-cover blurb, gets you hooked then you're more likely to read the rest of the book and/or probably buy it or recommend the author to someone else.
The translation is along the lines of "If you agree with or like the setup, you'll go along with with the rest of the proposal."