The more relaxed and friendly the escort seems, the quicker we will be comfortable. It's easy to say "relax and be yourself" but if you can that is what works.
I think the last thing you want to do is talk about a client's nervousness - that would only make it worse.
As someone else said smiles go a long way. Some girls have a gift of chatting and breaking the ice and will find something for us to have a laugh about early on, but if that is not your personality, don't try to force it. If you manage to give the client a feeling that you are happy that he is here, that is probably the most important thing.
From what I remember, Dieve, this is not a set of skills that you need to worry about!