Choices of question style
Closed v. open
Closed questions permit only 'yes'/'no' answers. They may therefore be more threatening than open questions because they leave no room for expansion or explanation. The questioner needs to decide if it would be more tactful to ask：
Have you finished that report yet？
Or
How are you getting on with that report？
The first question implies that the report is now due； the second merely asks for a progress statement. The open question allows the respondent to elaborate and does not have overtones of authority.
Wh- type questions
Questions starting with question words： what， when， why， who， how， are open questions but they are also very direct. Too many questions like this have the flavour of an interrogation and may make the person being questioned feel uncomfortable. It may be necessary to preface the questions with phrases that show the questioner is aware of the intrusiveness of the question：
May I ask you…
Could you tell me…
Would you mind telling me…
I wonder if I could ask you…。
I would be interested in knowing…
If it's not indiscreet， may I ask …。
I know it's not really my business， but…