Conservative canvassers want to zip quickly from door to door. So do your duty and grill them about the Big Society

When the doorbell goes at this point in the electoral cycle, there's a fair chance you may find a representative of the Conservative party standing on your doorstep, particularly if you live in a Tory hotspot. But, despite David Cameron's attempt to win over Guardian readers last week, you probably regard the Tories with much the same suspicion as Victoria Beckham regards a Mars bar. What to do?

If you choose simply to ignore the bell, you run the risk that it's actually your local Labour party candidate at the door – whom (it suits me to believe) you might at least wish to hear out. Or it could be your neighbour's rather attractive gardener seeking the proverbial sugar. So best give the curtains a quick twitch first before deciding whether or not you're home.

Tories are easy enough to identify, even if they're not festooned with blue rosettes: navy blazers with gold buttons, mustard colour cords and brick red chinos are a dead giveaway. As is a generous dollop of tweed. Such sartorial peccadilloes seem to have gained ground almost as widely among the Tory women as the men, actually.

If you opt to answer the door nonetheless, you will instinctively wish to send the Tory canvasser packing as quickly as possible. Try to resist, for reasons we'll come to in a minute. But if the very presence of a rightwinger on your doorstep gives you the creeps, just tell them straight that you don't share their political faith; that you'd rather swim naked in shark-infested water than vote Conservative.

They will then beat it nextdoor pretty much immediately – after all, a canvasser's job is not primarily to persuade, but to identify their vote so they can get it out come polling day. But if you are reluctant to be so blunt, using children (whether real or imaginary) as an excuse is particularly effective. Deploy the "sorry, can't stop now – I'm in the middle of changing the baby's bottom" line of defence.

But far and away the most effective way to deal with a Tory canvasser is to sabotage their plan of zipping quickly and efficiently from door to door. This is dead easy. Think of the issues that turn on your average Tory. Gay rights and the equality agenda? Er, no. Narrowing the gap between rich and poor? Not quite up there, somehow. Bolstering efforts to meet the millennium development goals? Well, not really if we're honest.

But just mention immigration or foxhunting or Europe and watch your Tory candidate spring to life. Then, after listening to a genuinely heartfelt speech for 15 minutes or so, perhaps try your hand at a few searching questions about the new Tory vision.

What will you personally have to do in the Big Society? How much time will that take (you're a busy person for goodness sake)? What exactly will the government do while you're working your socks off building this utopia?

Expect much "people power" rhetoric, lots of general waffle and a fair bit of foot shuffling in response. By now, you should have detained the Tory candidate for a good half-hour and you have more than done your duty. The political party you genuinely support will thank you for it, truly.