Stuck in a rut

So today was alright, it was a lab day, which I prefer over other days, because the students get engaged, and lecture is minimal. Of course, there needs to be a lecture to setup the lab and to get them going. My trouble is how far they make it when they are on their own in the activity. Then trouble is that they get stuck. Today I can sort of see why and its in the questions that are asked as they investigate. However, I was just out of things to say when I was trying to introduce the lab. So when I reflect on this, I tell myself that I know I can do better, but how? more later...