I’m totally writing this for myself but if it helps you - be my guest.
1. The most important thing is to remember that your first chapter is still a chapter so treat it like one.
Think what a chapter in your story is. Is it a single image, a one scene or a whole arc with beginning middle and end, or something different. Your first chapter should be no different than any other.
So, my chapter is like a short story, and I like to have one big event that all the little events center around, it forces my character to act and change and it develops her relationship with one other character.
2. But it’s also different because it’s the first thing that your reader sees. Make a good impression.
Your first chapter should mirror the entire story in at least one aspect. Figure out what is your thing, which makes your story memorable and unique. Is it the poetic style, a sarcastic character with a strong voice or interesting setting? Start with that.
Think also about a theme of your story. Are you writing about tragic lovers, or loneliness, or the inevitable doom caused by capitalism. Give your reader a taste of that.
Back to the example. My thing is fairytale-esque atmosphere with lots of gore, and I write about complicated familial relationship in a royal setting.
3. Don’t focus on the first line… yet.
The thing is, your first line can be great but if it’s not at all connected to the rest of the chapter your reader will feel cheated. Lingering on the first line for hours is also not good for you, you must write the whole chapter, not only this one line.
Forget about the first line. Write the whole chapter then come back to it.
4. Start where the story starts.
If you don’t know where to even begin think about your entire story. What is the latest event that your reader needs to see to fully understand your story.
If you are familiar with the story structure you can think of the first chapter as the necessary information for the inciting incident.
You don’t have to fit the entire set up before the inciting incident. You can sprinkle it through next few chapters. Introduce the characters and information important to the inciting incident, so that your readers understand what is happening and move on.
My story’s big event is the invasion of dragons on the city and a terrible winter it caused but you don’t really need to see it happening to understand the story. It’s enough that I mention the consequences of this invasion. The inciting incident is mc losing someone so I should introduce them and show how close they are. The main story is mc dealing with consequences of something that she did so I should start with her doing that, or a bit earlier to set up the stakes so my reader understands why she did it.
5. Remember the scene elements: conflict, obvious immediate impact on the plot and emotional shift.
Every chapter, especially the first one should be interesting. Take care of this by ensuring that something happens in it that your readers will find interesting.
Conflict will prevent your mc from getting what they want too easily - this is plot. Make sure that what they do has an impact on the whole plot - this is a chain of cause and effect. Finally make it affect your character emotionally. If your character doesn’t care about what’s happening, then why your reader should?
Now that I wrote all these helpful tips down maybe I can trick my brain into listening to its own advice.
The chapter will center around the big party in the king’s castle. I’ll establish what rules her father made and her general personality. Then my other character will cause a situation where mc will have to break one of the rules and figure out how to avoid the consequences. She’ll work with this other character and change her attitude towards him thus developing their relationship.
It has conflict - mc avoiding the consequences of her action; impact on the plot - she may not be connected to the thing she did, but it still happened, and it will cause further conflict; and emotional shift - now my mc and this other character are friends. It includes royal setting, familial situations, and fairytale atmosphere - dealing with the dragon while the worst winter ever is happening.