OK, ladies, this is a fun thread, so let's not get too uptight...
What do you NOT do when crossdressed... You know, "guy" stuff that's unladylike.
I'll start: Do not fart out loud, just because it amuses the kids (for whatever reason, I have no idea)!
By the way, it does not have to be as vulgar as my opening example. You know, guy stuff that just doesn't go down well when crossdressed.
Have fun!