I write a lot of horror, and I notice that my characters use "Oh my God!" when they're frightened in my scenes by a demon, ghost or murderer. How can I make them seem terrified without being so cliche and using "Oh my God!"?
Try writing their thoughts of the moment, and how their body reacts (ex: heart beating fast). Also keep in mind that there are 3 ways a character can react to a scary event. Everyone's different so it depends on the personality you gave them. 1. The runner; 2. The fighter; 3. Frozen in spot.
For example the thoughts of a runner might be “I don’t wanna die, I don’t wanna die!! I need to hide! Omg omg it’s right behind me."
A fighter might sound like “Hah! You don’t scare me! Do you think that bloody knife can stop me from taking you down?”
And the frozen in spot is panicking in their mind because they can’t move their body.
Like I said above, it depends on their personality. Also your story will sound even scarier if you add more description and less dialogue. "Oh my god!” isn’t enough. Hope this helped a bit.
Good luck with your story! Can’t wait to see what you come up with!
If you want to express fear, or that someone is frightened, then try and show it, not tell it. If there are multiple people in the situation, then try to describe another person. For example, 'The color drained from Jeff's face.' If there is no one else, then describe how the character is feeling. For example, 'my heart hammered inside of my chest,' or 'I gulped down the lump forming in my throat.' Your character can have some dialogue, just as as long as you don't say, 'I am so scared.' Try and say something more like, "'You don't scare me,' she said with a wavering voice." This is so you can tell the person is scared, but brave at the same time. Characters dialogue can also help develop their personality.