jmichaeliii

I struggle with it too as I don't want to come off as a sleaze bag.
I have had the most success developing rapport and setting the appointment without getting into specifics.
I then tend to "test the waters" in a first meet to see whats Ok and have been lucky enough to forge a few really nice long term client-provider relationships.  Admittedly it took a couple sessions for barriers to go away.  My experience has been once both parties are relaxed with one another, great things start happening!  I love my sessions with my regulars.  That initial patience has paid wonderful dividends. 

I think it's like any relationship in life.  You build a rapport with each other, there is a consistency with how they treat you.  I think after awhile your gut will tell you.
I have 2 guys I have seen for a year and I trust them totally based on what our interactions have been like over that period.
You can always be wrong, but that could be with anyone in life.