One thing to remember before your appointment and testing,...and this is especially important for females, as there appears to be a male bias on the diagnostic process,...so be your true self. When I say this,...even if you have to be at your worst,...no masking/camouflaging behaviors. What we know from the autism genome project is that there appears to be a phenomenon where females need significantly more "genetic loading" before they become diagnosed,...and this is not because of some X-chromosome (female) protective effect,...it's because of the testing and interview methods. Females often will exhibit "subclinical" symptomatology,...primarily because they are so used to hiding their symptoms in front of other people, they don't remember to turn off their masking in front of the psychologist,...and then "they don't have autism".
So,...what that means is,...prior to going in,...no medications, no caffeine, no nootropic vitamin/herbal supplements. Furthermore,...and this is the hardest part, because we were all taught to be friendly, polite, receptive individuals,...if it is a bit of an "act" for you,...stop the acting in front of the psychologist.