Go back and get some more information and techniques. Until they have a real solution to the original problem that works and they are confident in. What I try to teach in the more advanced classes is a confidence in their ability to go through this process. I used a lot of these skills when I worked as a consultant. An underlying theme that I try to convey is a comfort with numbers.
Clear communication is the first one.
After I have looked at how they say what they are saying, I look at what they are saying. I ask to what depth do they understand the material. It is a non-straightforward applications step. I look at the effort expended and where they started and where they ended up. My expectations for students who come in with a lot of background are much higher than for those who come in without the background.