The article presents information on how automobile insurance works and how one should buy insurance coverage for one’s car. One should review one’s insurance company and one’s insurance coverage, then make changes to lower one’s bill. Many drivers can save more than $1,000 a year by switching insurance carriers. Simply dropping or changing some coverages can save one lots of money. According to the Insurance Information Institute, an insurance trade group, policies break into six main coverages, each with its own premium: Bodily injury liability; Property liability; Collision; Comprehensive; Medical payments and Uninsured motorist. Many factors dictate insurance costs, starting with one’s address. Costs differ markedly by state and locality. Rates can even differ between neighborhoods within a city, depending on a variety of factors, including frequency of car thefts and break-ins. Also, if residents of a certain city are more likely to sue, rates will be higher there. Age, marital status and frequency of driving also affect insurance costs. In general, the younger one is, the higher the rate, and the older one is, the lesser the rate. Insurance carriers rate cars first on value: The more expensive the car, the more costly collision and comprehensive insurance will be. Carriers also charge more for car models most often involved in crashes. And rates are higher for two-door coupes and other sporty cars that insurance carriers expect will be driven fast. INSET: THE RATINGS GAME.