The key is to be relaxed yourself and to get her to relax as well. Some girls clam up because they're strung up and stressed out about you being a customer. They draw a clear line between themselves and you.

So you do everything in your power to make them feel relaxed, then the conversation will flow.

Humour is great, but don't be a smart arse or be sarcastic. Be sharp, pick up on something that you can slide in a flirty remark or joke that also praises her. Let her know you find her attractive. Like one ML said to me she worked part-time as a cleaner when I asked if she did anything else like study. That was the perfect opportunity to make jokes about sexy maid services.

Or you can make self-deprecating jokes. Being able to put down yourself for the sake of a few laughs is a good way to show the girl that you're easy to get along with.

Making a girl laugh in a way that makes them feel good about themselves is the best way to make them loosen up.

You can sprinkle a bit of serious talk like something about current affairs, especially anything that might impact on them. Any news you might have heard from their home country, news that impact on her demographic, etc. Not too much serious talk, though, cos it might make you forget about sex. That actually happened to me a few times with more chatty girls!