Owning an aircraft brings with it a number of responsibilities, one of them is making sure that your aircraft is insured properly for damage to the aircraft, third party and for liability.
You will need extra coverage when more than one pilot is flying on your aircraft, do also include any flight instructor if you are planning to do any kind of flight or recurrent training, be that VFR or IFR.
A good insurance policy covers at least these areas: hull, medical, liability, pilot experience and aircraft use per annum. We will discuss them below.
Hull coverage protects you from loss or damage of the aircraft, for this you will need to state the value of your aircraft. This value changes with time as you add equipment like new EFIS panels or upgrade avionics or the upholstery. Do not forget that if the aircraft gets a new paint job its value will increase too.
In case of a total loss of the aircraft (usually when repair costs more than 70% of hull value) the insurance company becomes the owner and you will receive the insured value. Stating the aircrafts value must be done accurately, under-insuring will lead to you not being able to buy the same aircraft again after a total loss. And over insuring will lead to a higher annual premium and other problems should any repair be necessary.
Exceptions to this policy are damages caused by normal wear and tear, normal aging, mechanical breakdown and any damage by ingestion of sand, stones and the like by engines or propellers. These are considered caused by normal use of the aircraft and must be taken care of by maintenance contracts.
Medical coverage is needed when you as the pilot or any passenger receives an injury during an accident and provides for coverage of related medical expenses not covered by your own private medical insurance policy.
Liability coverage takes care of problems if you have third party property damage or even bodily injuries. These costs can easily run into the millions. Policies can be set for liability per occurrence or for a single limit and also for any passenger. You will really need this type of liability insurance.
Check with your insurer if any legal costs are included and if you have protection against aviation authorities enforcement actions. A loss of license policy can be one of them, important for commercial pilots.
Insurance companies will ask that you comply with what the aviation authorities require to keep your license valid to be insured. Expect additional training requirements when you fly pressurized aircraft, turbines, and larger twins.
Any extra training, an IFR or multi-engine rating, low accident history, experience in flight hours on type and annual recurrent training for the pilots will eventually result in a lower premium. If any one of the pilots in the pool has a substantially lower level of experience then this may result in higher premium than expected. Additional training, ratings and / or flight time for that pilot can be beneficial.
A special clause in many policies is the open pilot warranty, which allows pilots without being named in the policy to fly the aircraft occasionally when they have certain minimum qualifications. Which can be helpful for CFI's or examiners when performing biannual proficiency checks or flight training.
If the aircraft you plan on buying is unfamiliar to you or your pilot then work with your agent on a training and transition plan for the pilot with a flight school and instructor that has intimate knowledge of the type.
Aircraft in use for fun and private flying will have usually a lower premium than aircraft in use for commercial and or airline transport operations (renting or charter flying).