Christmas is coming. Again.

Well, in fact, Christmas has been under way since September as far as the supermarkets are concerned. As always, mince pies and Christmas puddings with expiry dates in November line the shelves.

I'll leave that aside though. It's an annual gripe of mine.

This year, Christmas is heralded by an increase in cold-callers trying to sell undefined crap for unrevealed prices. Those selling stockmarket shares are particularly active at the moment. They have adopted TV stockbroker-type voices and tell you all about this wonderful share they have discovered, which will double in price within minutes after you buy it. They never actually tell you which company this is, nor how much the shares will cost. I assume they will reveal this information after you hand over your credit card number.

Then, no doubt, you will find you are now a majority shareholder in a Patagonian sheep-milk conglomerate that's under investigation for selling watered milk, and the Patagonian Department of Agriculture would like to speak to you.

Two tips here:

1. Never, ever give your credit card or bank details to someone who phones you. You have no idea who they are. If they are legitimate they will give you a number where you can call back.

Don't call back.

2. If I knew of a company whose shares were certain to double in value within days, I wouldn't tell you. I'd be buying as many as I could myself. I might phone you to ask for a loan so I could buy more, but the profits are all mine. If some stranger wants to sell you shares in a hurry, he's offloading junk. There is no other reason.

I expect these calls will increase in the run-up to Christmas. Since they are paying for the call, here are some ways I have entertained myself with them when they call.

1. Say 'Hello'. Wait, ignore everything the caller says. Say 'Hello' again, in a questioning tone. Become more agitated with each 'Hello'. Add in 'Is this some sort of sick joke?' and 'Why are you doing this to me?' Don't sound angry. Sound persecuted. Give the impression that you are constantly hounded by silent calls (remember-ignore everything the caller says). Don't be the one to hang up. Make comments away from the phone such as 'Have you traced this yet?'

The longest a caller has lasted on this one is four minutes, twelve seconds.

2. (in a pathetic voice) 'Will you be my friend?' Ad-lib from there. Sobbing is good. On no account get drawn into any conversation about whatever they're selling. Mention your cat/dog/hamster that died today. Steer the conversation into pets, and how pet shops never tell you that animals have to be fed. Be graphic. If they persist, say you had a child once. None have ever waited to hear about that.

3. I once had a caller try to sell me double-glazed patio doors. I kept him on the line for around half an hour, discussing the various merits of uPVC and wood, then asked how they would cope with the drop between my living-room floor and the garden. He said they could fit steps. I asked how many steps I would need from a fourth-floor flat to the ground. He hung up. I could have taken the easy way out and told him I already have patio doors, but where's the fun in that?

4. For all double glazing salesmen: ask for a written guarantee that their windows will block alien mind-control rays. Say you have been affected by these in the past and they have made you do terrible things. You want the guarantee to include company liability if the double glazing doesn't stop the voices and the blackouts. If you ever manage to get a company to agree to this, let me know.

The aim in all of these is to get your number listed by these callers as 'nut'. It won't stop them all but it does, gradually, reduce their frequency. Unfortunately, every time you move house it starts all over again.

Still, everyone needs a hobby.