Mystery, romance, science fiction or fantasy, there are four things that your opening scene has to do.
Create a contract with your reader.
In the opening scene, you tell your reader what type of story this is going to be. No, you don’t come out and SAY but a humorous scene promises humor throughout. A world of dragons creates an expectation for magic. If you open with a chase scene, people expect action. Your opening scene is a taste of what is to come.
Introduce your character.
Before we can care, we need to get to know this character. What do they love? What kind of person are they? How do they interact with other people? Show us what matters before you shake things up.
This doesn’t mean that the main character has to be saintly, but it does mean that they have to be intriguing.
Introduce your setting.
If you are writing fantasy or science fiction, you aren’t going to have time to do all of your world building in the opening scene, but set the scene. Are we in a lunar station? On a world full of dragons? In a dark, dusty mansion?
Some books get manage to subvert this one. In Harry Potter and the Sorcerer’s Stone, Rowling opens in the muggle world. Yes, we eventually get to some fantasy but it took longer than most fantasy lovers appreciated. But it worked well for people who were new to fantasy.
Hooking your reader.
Last but not least, the opening scene has got to hook your reader. Do this by getting their attention and making them want to find out what is happening in this story. It could be your intriguing setting or your compelling character. How you do it will depend on your story.
It may sound like a lot to get done in rather short order, because it is. But it is essential to keep the reader reading. It will probably take you several tries to get it write . . . I mean right.
–SueBE
One Writer's Journey 