From what I had read, there is really no way/reason to prep for an IQ test, since it does not measure knowledge. I was told to just make sure my DD got a good nights sleep and a normal breakfast. I just told her that she was going to go meet with someone who was going to identify how she learns. (we explained that we wanted to know how best she learns, so we can make parenting and educational decisions with that knowledge)

HTH :-)