Many people have described and used these learning activities. My attempted contribution is to explain them where they fit into education.
Discovery of Structure
What are the properties and characteristics of a fruit? I don't care about fruits, the issue is how you would answer this question -- how would you discover the properties and characteristics of fruit? You would have to examine several fruits, and discover what they had in common. (There would be an implied contrast to things that were not fruits.)
Reality is not so kind as to make all fruits the same. So at an advanced level, this assignment could involve discovering exceptions (the strawberry has it seeds on the outside) and subcategories (some fruits have many seeds, some have a pit). Once a category is discovered, it is exciting to discover unique members of that category (such as the longest day, or a fruit with the seeds on the outside). It is useful to learn this advanced level.
But your first concern as a teacher is the basic idea: (1) the world can be grouped into categories; (2) we can and want to describe the properties and characteristics of those categories; (3) we do that by observing instances of the category and noting their similarities, and (4) a description of a category is not intended as a description of any particular item in that category, but instead represents the commonalities in the category. When scientists describe the moon, they describe our moon. But when they describe a thunderstorm, a mammal, an eclipse, or tides, they are describing commonalities.
Students can take their studies as a meaningless collection of statements. But if they are to understand what they study, they must know that the moon, our government, or the Revolutionary War are descriptions of specific objects or events; and they must know that thunderstorms, mammals, etc., are descriptions of categories. They probably need some sense of how the descriptions of categories are constructed. Imagine a student who does not know where the information is coming from, or how it was constructed, and does not care. That student is probably trying to memorize meaningless facts.
So, in order for students to better understand what they are learning, to better use the information they are being given in the classroom, then need to understand about the discovery of structure.
How do you teach this? You can try explaining it, but I don't think that will work -- your student probably needs to already understand the concept in order to understand your explanation. Anyway, you want to develop a mental model, not memory. To use the problems-first method of building mental models, you simply give your student 3 fruits and ask them to describe what the fruits have in common. You might have to do some explanation in the context of this problem, but only if your student needs it, and then your explanation is in the context of solving a problem, which is when explanation should occur.
Things you could do this for: fruit, leaves, ink pens, drops of water, sunsets. At an advanced level -- three falling objects. At a restaurant: 3 pieces of silverware, or the waitresses (in contrast to the other people in the restaurant).
Components of the Discovery of Structure
Description. I do not like to think of description as a basic activity of science. From my perspective, the point of science is not to describe objects or events, the point is to discover the underlying structure. However, description is a building block of discovering structure. The idea is that given some object or event, a person should be able to produce a very lengthy description of it.
As far as I know, you teach this just by asking for descriptions. You can ask about anything, in theory; in practice, you might not want to ask for something with a lot of detail. Things to describe: a drop of water, your finger, a piece of wood, a fork.
"Dissection". To discover structure, it helps to take things apart. I assume students do not need to learn this.
"Experimenting". Part of describing something is listing how it reacts to things. For example, description of a drop could include what it looks like when it is wiggled. This is not a formal experiment, as the word "experiment" is now understood by scientists. But it fits a simple notion of experimenting.
This too seems to be natural and not in need of teaching. However, finding interesting manipulations requires creativity. For example, if you were trying to describe a dog, you could discover that dogs chase balls, but only if you thought to throw a ball.
Explanation
One of the basic activities of science is explanation. This you can start at a very early age, simply by asking children to explain. In a restaurant: Why are there empty tables? Why are the waiters and waitresses all dressed alike? Why is the manager dressed differently? Why does everyone sit at their own table? Why do they have menus?
Your goal in doing this is simply to provoke the activity of explanation. A correct answer does not matter. Once the child has provided the explanation, the teaching moment is over. You can nod sagely, or look surprised, or appreciative, or whatever. (You probably should do the same for any of these activities of science.)
Testing
The third skill I will call testing -- how do you test your ideas? The basic idea works for one-year-olds: "Check". If you think something is true but you aren't sure, do you want to spend the energy to check? Or, to give a simple example, my eight-year-old wanted to take another candy for her sore throat. I told her you could take the candies only every 6 hours. She went and read the package and reported back to me the true value (which was less than four hours).
Of course, the advanced skill is how to perform a formal experiment testing the relationship between two variables. None of the children I teach are ready for that.
Another difficult skill is testing a theory (or explanation) by deriving the predictions of the theory. I don't know when children start doing this.
A skill young children can learn is to test a law. I suspect this is natural for them -- they live in a world of rules, so it is very important to them to test rules. Some of my favorite examples. Her aunt told my daughter that any number of people could play a particular game. My daughter asked if eight could play. No, my aunt explained that there weren't enough supplies for eight people, it was any number six or less. My daughter asked if one person could play. Another daughter, when told that God loves everyone, asked if God loved Satan.
