You'll hear this from a lot of bros but it's about rapport and how you make them feel. If you make them feel that you're a sleaze and a bad guy in general, they will not do you any favours.
If you're a gentleman and connect with them on more than just a financial level, they are more likely to go ahead with you're request.
A tip from me: always try the first pic with BOTH you and her (can be a little tricky with an iPhone). This will give her a sense of security that you are less likely to paste it all over the interenet cos it's got your face on it too
But mainly, it's less threatening. Once she's warmed to that take more pics and remember, they DON'T have to be nude pics.
If it's a company policy (like in China MPs) that they cannot take pics then just respect that fact...
