How to be Insulting in Hotels: Call room service last thing at night, when the kitchens have just been locked, and ask for a cheese sandwich and a glass of fresh milk. Make sure that you leave them untouched and conspicuous the next morning.
How to be Insulting Abroad: Insist on paying for everything in sterling.
How to be Insulting in Banks: Put your old sandwiches into the night safe pouch and complain by letter when it's returned to you empty.
How to be Insulting in Church: Always try to be half a line ahead of the vicar, and always be as loud as you dare in the responses.