Your harassment policy should point out that the law doesn’t prohibit simple teasing, offhand comments, or isolated incidents that are not very serious. Also, there is no harassment if your coworker over hears something which is not meant to be heard by her and is not about her. "Harassment is illegal when it is so frequent or severe that it creates a hostile or offensive work environment" (quoted from our policy).
If you are really asking how do we condition ourselves not to make loud, off-hand comment constantly, you all need to call each other out in a SERIOUS manner. Do not joke, just speak up and say " I believe that's inappropriate" then offender apologizes and tries very hard not to be called out again.
You all may think this is really dumb, but look at it from two angles. (1) Does your company want to get sued, sorry that's what lawyers do especially in the US (2) Pick something you don't like about yourself, say you have some weight on you, and then have someone call you 'lardass' and comment how they'll need two chairs for you to sit on, or we shouldn't to fast, so you can keep up. Have them comment on how being fat doesn't allow you to do your job properly etc. and have them do it constantly. Then tell me if that's a fun place to work and I'll tell you that they're just teasing, and where's your sense of humor?
"I am, therefore I am." -- Akira