As my agent reminded me, a first page has to do so many things, e.g. set the time and place, introduce the main character, set up their motivations/dreams/desires, start the action, allude to where the book is going, etc. It’s one of the hardest things to do, although thankfully it’s possible to do the best revision of the first few pages at the end of the writing process, when you can pull everything together. There are some useful tools to help.
You can find a great post here by Livia Blackburne on WritersDigest.com on why agents stop reading your first chapter. At the Boston Book Fest, submissions were read out in front of everyone and agents made comments. Most common turn-offs included generic or slow beginnings, trying too hard or providing too much information. Read the full article below.