How do we help our kids not expect to get everything they want all the time? Is there some sort of social trick maybe? Some sort of long drawn out explanation of life and how things work in adulthood?
Not really - just don't give them everything they want. It's called "saying No."
Have you heard of those "fiver parties" starting up now? Where all the guests bring $5 to contribute to one large gift? This is an attempt to have the child not worry about gifts, and they still get the anticipation of the big gift that's coming.
While I don't really object to this type of party if it's what you want to have, why not just tell all the guests that no one's obligated to bring gifts at all?
There's nothing wrong with not expecting gifts. Problem solved.
We've got all sorts of things we're diagnosing our kids with and all sorts of things we think might help, and might work with them to help them understand.... Sometimes it's a far simpler solution.
Saying no when they need to hear no.
Being kind when they need kindness.
Expecting them to be kind.
Expecting them to have manners.
Giving them something productive to do each day.
Sometimes things are nowhere near as complicated as we want to make them.
We don't have to always be looking for the next big extraordinary method ... just keep it simple.
**disclaimer** none of this is in reference to kids who truly have some sort of mental or physical problem that changes their entire world and way of interacting with their world.