Etiquette rules for guests

I thoroughly enjoyed watching the wedding today. The hats and outfits worn by the guests were amazing.  Meghan's mum looked so dignified and it really can't have been easy for her. I wonder if she has been swotting up on etiquette rules.  I have just been reading etiquette rules for house guests.  I had to smile at a few of them. One of the rules mentions looking into your hosts bedrooms without permission.  I would feel very uncomfortable if I thought my guests were snooping around in my bedroom. Why would a guest be so rude as to do that?
Tony and I are off to a ceilidh with a red/white/blue theme this evening. I have the red/white and blue outfit I have the handbag, purse, scarf, belt and flags. I even have a union jack hessian bag for carrying the picnic supper in....  we do like a good ceilidh.