Here's a quick tip to get your thoughts flowing on the very first page:
Curiosity killed the cat.
Am I right? You know I am. What I mean is this: Stay away from back story on the first page.
And there are many other reasons I could list.
As a literary agent intern, this is something I read A LOT on first pages. But, it's something that should not be there! I want to be in the here and now. This isn't to say I want dropped right in the middle of action. This confuses me. I want to know what's going right now, at the very moment the MC is experiencing.
No explanations, or why's or how comes. Just show the present. There's plenty of time for explanation later.
See, if you write subtle hints and drop enticing clues as to what happens next, the reader will be turning the page to find out.
Peak the reader's curiosity to find out why, or what, or who, and you've done a fabulous job on the first page.