How to be insulting at the library: Find the coziest reading nook and start snoring.
How to be Insulting in Theaters: Noisy wrappings on sweets can be unwrapped at moments of tension when the rest of the theatre is silent.
How to be Insulting in the Street: Walk along as if you have stepped in something unpleasant, by pretending to scrape your feet along the pavement, or rubbing your soles on any available patches of grass. Then look daggers at anyone walking a dog.
How to be Insulting in Church: Sing out of tune in all the hymns and try singing half a line behind everyone else.
How to be Insulting at Christmas: Refuse to give any guests a drink, on the grounds that it's for their own good not to drink and drive. Have plenty of soft drinks to offer them though. Then pour yourself a large Scotch, on the grounds that you aren't going anywhere and don't have to worry.