Firstly make sure you're covered for your test drive via the dealer or the private buyer. Then as soon as you decide to buy the car, shop around for insurance – most dealers will take a deposit (make sure you get a receipt) and save the car for you while you do this.
You can pay your road tax by monthly direct debit, or for six or twelve months. Although it is no longer a legal requirement to display a valid tax disc on your windscreen, you are still required to tax your vehicle every year. When the tax has run out (DVLA will send you a renewal reminder) you need to apply for a new one by filling out a form (V10) at the post office and producing your vehicle registration document, a valid certificate of insurance and an MOT certificate. With the right documents you can also renew your car tax on the DVLA website.
A valid MOT certificate is required when a car has been registered for three or more years. This requirement starts on the vehicle's third anniversary. An MOT costs a maximum £54.85 for a car which seats up to eight passengers; you may get a cheaper price by shopping around. The certificate is valid for twelve months from date of issue.
In the first year of driving, one driver in five is involved in an accident. On top of this many cars break down because of poor maintenance. So if you want to ensure someone will come and fix your car at the roadside at any time of day or night, or tow you to a garage when you can't start up at home, then you need breakdown cover. AA Driving School pupils get a great deal on breakdown cover.