How insurers may try to trap you:
A) Keeping you as a captive customer
Car insurance is a highly competitive business. Many insurers offer substantial discounts to motorists who switch to them from a competing company will once they have you as a client they will most probably want to keep you for as long as possible, and to sell you as many of their services as they can. A common tactic is to get you to pay by credit card and then inform you that "for your convenience" they will hold onto your card details so that your next premium can be paid automatically without you having to concern yourself with it. What they do not tell you is that the renewal will be at full price and will not include any introductory discounts that you have enjoyed in the first year.
They are therefore hoping that you will simply shrug your shoulders when the renewal form arrives a year later, and that you will allow it to go through automatically, blissfully unaware that it is for a far higher premium than you paid a year previously. You should not fall for this; refusing to allow them to carry out an automatic renewal leaves you free to find a possibly cheaper alternative, whilst it does of course place the onus on you to make sure that you have a replacement ready for when your current policy expires.