Well you need to experiment on the day because it's impossible to say because the weather conditions on the day vary so much.
I'd say if it's a dry track with decent weather start at 22psi front 24psi rear and just use that as a starting point. Do a session on track and as soon as you pull into your garage check your pressures, you want to get as close to 30psi as possible.
If you end up with over 30psi when you come in drop them for the next session or raise them depending on what the pressure gauge is telling you.
Also don't be afraid to experiment, some people go out with around 18psi in their tyres and this can affect how fast they come up to temp and how fast they "go off" as such. After a few sessions you'll know exactly what works best for you.
Ao48's are a brilliant tyre. I'm sure you'll have a great day!