ACT Compass Writing Test (If YOU have taken this please leave comments)

I’m going to be taking the compass test towards the end this month. I have a lot of concerns on what to expect on the writing test. When I took the writing test for the ACT I did poorly. Has anyone taken the writing portion for the Compass test. I seem to have this problem of not having anymore ideas to write about. My mind goes blank. Does anyone else have this struggle. How do you master writing off the top of head? What sort of prompt should I expect? How is it graded? The bottom line is, how can score high enough to be placed in college level courses?