If you need some personal information (From a customer) that can create some troubles.. How do you tell him/her this?

I suggest that you re-assess your needs.

Catch him private and discuss personal things not during working hours by approaching professional way

   There are some contracts and documents must Takhadd s personal information about the customer, such as

                                                                     Health insurance and patient records and travel bookings, hotels

Not that easy, nobody gives their personal information and that too after knowing that it's going to cause them some trouble.

Step by step.  Start talking in general and then after a while you will find that some sort of confidence and trust raised between both of you.

Don't raise the subject directly just point to it in away or another and let him talk then start getting deeper in the subject showing that it is something interesting.

IF topic was annoying ,so don't proposes