How to ...

Payment is to capitalism what sex is to evolution: they're both the vital moments of exchange and, interestingly, moments of extreme pleasure. With sex, there is the moment of orgasm; with payment, there is the moment you get your carrier bag.

When paying, you can give the exact money or a big note. Fiddling around with change implies that you've scrimped and saved for your newspaper; giving a big note implies that you've just been paid. Some people insist on giving a big note together with some change, so the shopkeeper will give them £1 coins back. Newsagents hate people like this, and often remove the magazine from the paper to stop them being so smug.

Shopkeepers hate change. It's heavy, dirty, and an average newsagent lifts a total of three tonnes of it every day. That's why they don't like getting your change and they don't like giving their change. The only thing they like is tuppences, because they never bother getting these from the bank.

Lots of prices end in 99p, but buy two of these items and they're stuffed. Always check your change while your hand's still out: 99 times out of 100, you'll get the right change, but it's worth spending a few minutes checking for 20p pieces from Guernsey, which are that island's largest export.

The difference between a debit and a credit card is that a debit card spends money you haven't got now and a credit card spends money you haven't got later. The good thing about paying by card is that you pay to the exact penny and don't need to carry a pocketful of change. The bad news is that you'll never be able to park again.

The lighter money is, the more likely you are to spend it. In the old days, a penny was the size of a baby's head and weighed as much as a small piano. It was not, therefore, something you frittered away on sweets. A credit card weighs less than an ice cream wafer, and is correspondingly easy to waft about.

Barcodes are the DNA of non-living things. Instead of you and the shopkeeper happily reading the price together, your item is snatched from you and scanned. Then you both look at the little read-out on the till that says, "Water, £1.80." If these displays were linked to the Highways Agency, they would read Tiredness Can Kill, Take A Break. You could then go to a coffee shop and have your muffin scanned.