When the premium is not mandated by the government, it is usually derived from the calculations of an actuary, based on statistical data. The premium can vary depending on many factors that are believed to affect the expected cost of future claims. Those factors can include the car characteristics, the coverage selected (deductible, limit, covered perils), the profile of the driver (age, gender, driving history) and the usage of the car (commute to work or not, predicted annual distance driven).
It’s important to note that every company considers credit very differently, and even among insurers this factor fluctuates by state. For example, NerdWallet’s 2019 car insurance rate analysis indicates that while State Farm charges higher rates for poor credit in many states, it doesn’t seem to do so in Maine. Similar variations are true for many other companies as well.
Minimal insurance policies cover only third parties (including the insured person and third parties carried with the vehicle, but not the driver, if the two do not coincide). Also the third parties, fire and theft are common insurance policies, while the all inclusive policies (kasko policy) which include also damages of the vehicle causing the accident or the injuries. It is also common to include a renounce clause of the insurance company to compensate the damages against the insured person in some cases (usually in case of DUI or other infringement of the law by the driver).