I noticed in my novels that I start with dialogue. If I started it with something else, its not too long after that there is dialogue.
For me, I get bored with too much description in a novel, therefore, I tend to write as little as possible. I've had CP's tell me to add more, and that's fine because they are reading it for the first time.
As for backstory, I try to add it within each character's POV whenever appropriate.
Example: She hated when John touched her back that way. It was something her father always did when he was lying to her mother and wanted her to go along with him. So she couldn't help but wonder if there was something in John's touch she should be aware of.
How do you start your novel?