For example, I had a list of ten questions on a page. Questions like:
What is the fastest mammal? Name three constellations. Who was Patrick Henry?
The "rule" was that when the kids had answered all the questions on the page, they got some treat (a night out, ice cream, etc.)
But the trick behind it was that in the quest for their answer, they would become engrossed in the exploration, learning all kinds of things along the way.
I never finished the curriculum (I had added Bible verses, activities and character traits to go along with the questions), but my mother gave me a handy set of some similar questions last week.
"Brain Quest". They vary in difficulty, and I think you can get them for different grade levels.
My kids beg me to ask them questions. As I ask, I try to engage them a little further, if the question allows.
If we run across a particularly interesting fact, I may suggest that they look up further information about that subject.
I try to remember: It's not in how much they know, it's how much they want to know, and whether they can find it!