I personally haven't tried this technique but I have read about it:
Some say to dip the clear part in some Future floor wax. Let the part dry preferably overnight. Then they say you can glue the part in place using regular glue without having to worry about the clear part fogging up.
However as stated above I have not tried this technique out yet. You may want to experiment with some old parts from another kit first.
Like Jaime, I have used Testors clear parts cement on a regular basis and had good results with it when gluing on clear parts.
I even used it to make some of the smaller side windows on my early TBF-1 Avenger build.
Hope this helps...