a mother's words of wisdom:
Be aware of how a man treats his mother. it will give you a good idea of how he will treat you.

those words are so true.
its similar to the whole thing of 'if you want to get a picture of someone's true character, watch how they treat those below them (eg servants) who they have no reason to be civil to'

a mother, ironically, is the person we tend to take for granted the most, and often does not naturally and intrinsically demand the same respect a father might.
if a guy always treats his mother with respect, he will most likely treat all women well, regardless of the circumstances. But if he is dismissive of her wishes and disrespectful in his speech, he is more likely to revert to similar behaviour when you fall into his bad graces.
(of course there are other things to take into account. but think about it. a good something to keep in mind)