on the original question, my opinion is i agree. the way a man treats the original women in his life is a very good gauge of how he will eventually treat his wife. but i won't generalize here. siguro may percentage na di applicable ang kasabihan.
on the waiter thing, i agree also. actually i think how a man treats waiters and subordinates or those who have lesser in life is not only an indication of a man's character, its an indication of a PERSON'S character, male or female, whatever the age.
My papa says before, you will know his character by the way he treats the waiter. you will have an idea how he will treat that are less fortunate than him. dito makikita if matapobre ba sya basically yung overall personality nya.