The exercises work best of the students work in pairs. One student "drives" the computer and the other student reads the instructions and writes down the answers on the worksheets. This kind of collaborative problem solving leads to explanations and discussion. Also, the instructor is generally not required to intervene and help as much. However, more than two students in a group leads to considerable extraneous discussion because one student is always bored.
The best situation is to run the labs yourself. However, if you are using graduate student TAs to run the labs, use TAs with some experience and interest in experimental psychology (e.g., not clinical graduate students). It is best if the TA is willing and wanting to learn how to use E-Prime and Statview.
Worksheets are designed to push the students to reflect on the underlying function of the various steps they are going through. Do not skip these worksheets.