Diplomatic language

A good way to be more diplomatic is to use the passive voice because it focuses on the action, not who did it.

I understand you didn’t finish the report. → I understand the report wasn’t finished.
Martin said you need some help. → I was told you need some help.

If you can give me the report at 4pm, I will be grateful. → If you could give me the report at 4pm, I would be very grateful.

Are you asking me how much it costs? → Were you asking me how much it would cost?

I hope you can finish before we leave. → I was hoping you could finish before we left.