My experience has been that if I hit 50%+ on a practice test that I'd do very well on the actual.
The Humanities general is probably one of the harder of the generals but I'd feel very confident with 65-70% practice runs.
Remember, due to the nature of these exams, you don't have to be able to answer every question correctly in order to score very high. I've left a CLEP thinking I blew half the test and still come out with a very high score.
Myrtle Beach, South Carolina
BA, Coastal Carolina University
BSLS, Excelsior College
MA, MBA, MA, Webster University
MAIS, Western New Mexico University (due 2013)