I keep hearing this phrase "NO backstory in the first 50 pages".
Problem is ... what exactly do they mean?
Often you have to inform the reader as to the thoughts and reasoning of a character and that sometimes includes background information. ( Even the setting can be confused for backstory. )
When writers and editors say not to put back story in the first 50 pages, according to the people I then questioned on this after having said it, they are generally talking about adding paragraphs of info dump. And I have seen people do this. Paragraph and paragraph of why the main character is kissing the girl or fighting a bad guy. It bogs down the story before you even care about the characters or their plight. Not good.
A sentence or two, properly framed around a triggering event (such as the flowers at a funeral that remind the heroine of the flowers her ex-husband used to bring her) are more than appropriate. They do indeed ground the reader.
If it is normal for the character to think about an event extremely briefly, then by all means add it. If you have to go into a long diatribe, then cut it until later. (Or start the story earlier because you have begun too late. I did that in one of my WIPs. When I finally realized it, I went back and added a whole new scene and cut some of the later backstory explanation to a new comer in my story. The balance can be hard.)
If you need to add background details to make the storyline make sense, just hint at something being not right at that point and don't forget to find a good way of explaining it in short later. A well done back story will make a book good, a poorly done one will sink the ship.
Don't sink your ship, but don't forget to add the paint.
