Mr, Mrs, Miss etc when referring to ourselves?
I remember being surprised as a teenager when a friend of my father's declared that he would never say "I am Mr Smith." At the time I thought this would be perfectly normal, but his reasoning was that "Mr" is a title which you confer on someone else, and this would comparable to the Queen announcing, "I am Her Majesty the Queen." ("My Majesty ...."?)
This has stuck with me, and I never refer to myself as "Mr...." (except for those exceptional circumstances referred to above, equivalent to referring to yourself in the third person); although I do find it slightly irritating on some occasions when, after I've given my full name, this is taken as an invitation to call me by my christian name.
For Introducing our self in business meetings or in front of a crowd .
I'm "Mr." Randy Jumaquio
For closing letter and signing on.
"Mr." Randy Jumaquio (with our signature above the name)