Involve your friends in the story. For example, if you're telling 'The Bloody Mary' story, you can ask one of your friends to be the one who goes into the bathroom to try it out (in a pretend way, of course). This makes them feel more involved and amps up the scariness. Another way is to build up the backstory more. For 'The Haunted Doll' story, talk about the history of the doll in more detail, how it got to the attic, and who might have owned it before, making the whole situation seem more menacing.
Set the mood. Dim the lights or use candles. If you're telling a story about a haunted house, you can make the room feel like a spooky place. You can also add some sound effects. For 'The Girl in the Graveyard' story, you could play some faint wind sounds in the background. Also, use hand gestures and facial expressions to make it more engaging and scarier. For instance, when talking about the ghostly figure in the graveyard, make your eyes wide and look around the room as if the ghost is there.