Best way of going about overnights is meeting the girl for an hour booking. Fuck her, then socialise. Do all the right things as much as possible as if you would on a normal date. Then if she likes you then you stand a decent chance of getting a good discount off her normal overnight rate. If she gives you no discount or not much then basically she doesn't like you.
.. WG's will disagree with this on forums as it goes against the principal of earning as much money as they can. But in reality, some will, some won't... in my experience most have, but I'm not a bad looking guy and I do tend to get on really well with escorts - contrary to normal life I struggle to even approach random girls.
I've had loads of overnights, of which probably half of the escort's I'd never even met. Only one has been a bad experience, and it was fucking terrible.