First, study your behaviour

in order to change our behaviour, we need to know first just what that behaviour is. So before you start to do anything different ...

• For one week, simply monitor what you do in relation to shopping and plastic bags. Try not to do anything you wouldn't normally do - don't refuse bags, for example, if you've never done it before, and don't use reusable bags if that has not so far been your habit. If you do most of your monthly shopping in one week, do your monitoring in that week, otherwise just pick a typical week. Keep a simple log or diary for each day: for instance, '4.30pm, trip to Budgens, spend £22.50; bags collected 5; action on returning home, 4 bags into rubbish bin, one used as bin-liner'. Be completely honest with yourself! If you're already a habitual bag-refuser, note the number of bags you've refused / would have been given.

• At the end of the week, list (a) the number of bags you have collected; (b) what you've done with them; and (c) any bags that you've refused. Add it all up. And then go round your home and count all the plastic bags that you have lurking in your kitchen drawers / under the sink / in your IKEA bag dispenser / in the garage / wherever.

• Sit and think about what you've come up with.