Second, the world has to be immediate. It’s got to be all right there,
humming along and working at the moment the reader opens the book.

ASSUME the world. Plunge into middle of the scene in the everyday world
you’ve created. Don’t spend any time explaining it. Just have your characters
react to it. 

Two ways to really screw this up are the backstory dump and the infamous, “As
you know, Admiral.”

Backstory is why the world and the characters are the way they are. Writers
have a tendency to want to explain the rules and delve into their characters’
motivations right up front. Don’t do that. You’ve got time. Assume the
world—plunge into it.

Do not data dump fives pages of backstory into the beginning. In some
cases, a prologue is one way around backstory issues, but you can’t use them
just any time you want to. A prologue must be about a pivotal episode
separated in time and/or space from the actual story. It’s not just a way
around the hard work of getting backstory in.

Execute a backstory dribble by assuming that the reader knows the world
and letting the context define the terms, or by explaining them in the context
of a minor conflict. (The Ebook Backstory Dribble is available at BAMWriters.com

Examples:

Context:

It had been two weeks since his last seissa, but Charrtq’s scent was still mild
and pleasant. While rolling around in hot sand held no attraction for me, I
supposed if I’d had feathers, I would have felt differently about it.

Minor conflict:

“Let me use your tajj.”
“No, I just had it calibrated. Besides, my mother is supposed to riff me
sometime. Her brother is sick.”
“Selfish.”
I kept quiet at that. Every time Dale was unplugged from the web, it was
someone else’s fault and I had no intention of….

Science fiction writers are exceptionally good at this. Check out Challenger’s
Hope by Feintuch or any good SF writer.