I begin by explaining that one of the main reasons we want to know what types of soil we have is because certain types of plants grow better in certain types of soil, and as I remind my students, I have always wanted to begin a garden at school.
I inform students that we'll be going outside to collect soil samples. I assign students jobs for this investigation, a "getter" to get materials, a "chooser" to pick a location, a "digger" to do the digging, and a "shaker" to shake the sample. I remind them of expectation during outdoor investigations, and take them outside to collect samples. They need to bring trowels and Ziplock bags outside with them.
I allow "choosers" to take their groups anywhere they like on the playground, as long as I can see them. At our school, due to the hard clay of Arizona soil, most groups found their way to wherever there was mud because it was easier to dig in (and I forgot the shovels!)
Once they get their samples in their bags, we line up and head back outside.
Once we are back inside, I have them label their samples, and continue with the procedures. I ask them to think about what resources they could use to support their predictions. In my room, most students went for their How do we describe soil? organizers, and some went back to their science textbooks. There were equally appropriate.