How to be Insulting in Shops
Find a nice dirty puddle and get the soles of your shoes well and truly filthy before walking into any shop with carpets.
If it's raining outside try to get your umbrella and mac as wet as possible and then drip all over the counters and stands.
In food shops touch all the fruit, except the pieces you want to buy.
Try tasting as many different cheeses as you can and then buy a small piece of pre-packed imported cheddar.
Spend several hours in record shops listening to recordings of Wagner and then go out with a potted version of the main themes played by Mantovani.
In shops with elaborate window displays ask to see the least accessible article on display and then decide not to buy it after an assistant has performed contortions trying to get it out for you.