What is the secret formula for scaring someone [No cheap scares!]

[Kman]

You know, Is there any video tutorial how to master the build up?

Ehh... Not really. What I'd say is just look at things that pulled that effect off well and take notes on it. A great example of it would be SCP-087. The whole game is basically you walking down stairs, but yet it's incredibly scary simply for the fact that it keeps you interested. What I mean by this is every once in a while a random sound effect that sounds like it's coming from below you, or what I found really terrifying was the fact that every 5 minutes or so these shadows like things flash in front of you, but they're there for such a short amount of time it creates this sense of paranoia as you don't really know if you saw them or not. I'd just say look through movies and games that pulled it off well, you'll start to learn from them over time