Answer to PLS

In case you don't read The Spandrel Shop, go there. PLS asks about undergrad research. My answer to him:

Undergrads are the sole source of labor for my lab, and my teaching load is such that I simply don't have the capacity to do a lot of hand-holding. I need students that can be shown once or twice and that's it.  I have had a wide variety of students but they seem to fall into three categories:
1. Really excellent students. Typically juniors that have done well in their physics and molecular biology class and have the ideas behind our techniques down pat. They are well organized and can work independently, and do so, making the right decisions in vague situations.
2. Students I get too early. I had a student recently that I had to spend 30 minutes showing them how to pH a solution and how to use a pipettor properly. Moreover, they just want to know the sequence of how to do the technique and are concerned about getting the "right" answer. These are sophomores typically.
3. Overinvolved students. These students are in a bunch of clubs and activities. They may have the skills and knowledge necessary but lack the blocks of time needed to devote to the experiments. They shortcut or leave great cells behind to go to their band practice or whatnot.

We have a research requirement, so students typically approach me during enrollment period to work in my lab for credit. I'd love to pay them by the hour I often take more than I can pay proper attention to, so sometimes my research students are "given enough rope to hang themselves with".