How do you prepare for class activation? If you're only just photoreading, well, it will work eventually, but I suggest you help it along with a little previewing. After you photoread your materials, just thumb through them to see what's there. I find this forms a good basis for class activation even when you don't think you gained anything from the postview.
Mind-mapping during classes might help as well, though the freenoters might suggest well, freenoting.

KWLee