Jeannine,
Exactly! Although some believe the extra time putting a pretest together is not worth the effort, I would disagree. The pretest doesn't have to be comprehensive or lengthly, just sort of a "toe in the water" to see where the students as a whole are at. One way to approach it is to take the key learning objectives as the basis for the questions. A variation is to take one or two key objectives that are essential to the course and assess a number of questions based on a single objective. Almost any way you slice it, the results will invariably be helpful.
Barry Westling