Deciding where to start your story is one of the most important--and hardest--things to get right. After all, as a new author you're dependent on those pages being good enough to hook an agent, editor, and (later on) readers so they want to keep reading. There's a lot that can go into this decision, and I want to share some advice based off what I've learned from my personal experiences as I've begun writing my eighth book.
Most of my books have not only had changes to the opening lines, but for the entire scene. However, the last three books I've written I've tried something new--I've focused on finding a line that would hook ME before I've considered the rest of the novel. For me, just like writing the QL blurb, I have an easier time with this if I focus on nailing the first line before fleshing out the story.
One suggestion I saw that wormed its way into my brain and took up permanent residence is this: make sure the pacing of the opening scene matches what you'll see in the book. Obviously you can't always jump right into the thick of things, but if the pace of the book is really fast, find some way to show that in the opening scene, even if its a different activity or setting from what the character does later on.
I know that's a little jumbled, but here's an example from a recent popular book (it doesn't matter if you loved it or not. It was successful at getting people to pick it up, okay?) In 4th Wing, Violet is constantly in danger. This is demonstrated with the parapet scene right off the bat.
You can also do something that demonstrates the personality of the MC. Like in the Hunger Games, you quickly see Katniss' determination to do whatever it takes to save herself and her family as she breaks the law to go hunt.
The biggest mistake people make (myself included in my early books!) was shoving too much world building at readers right away. You gotta treat that like an onion and peel those layers back as needed. It's a delicate balance, but it's SO important.
If you struggle with this, try picking apart what you like from the first line/paragraph/page from novels that have sucked you in quickly. If you do this enough, you'll find the patterns and learn how to apply them in your own writing.