You should run them about the same as the standard alloys - check the handbook for recommended pressures.
It might be worth dropping them 1-2psi from that if it's icy or wet outside though, as you need all the grip you can get in this dodgy weather! But if you do high speed motorway miles then leave the pressures up and just be aware they might not grip quite so well.
30 sounds a little low - most people on here seem to run from 30-34 depending on taste. Best thing to do is try the tyres round a roundabout or two at each end of that range to see how they feel - decide which you like more and tweak the pressures between the two until you're happy.
I'd run the backs 1psi lower than the fronts though, as you get a bit more of a progressive breakaway at the limit then
