Summarize the following:
While it varies from company to company, you usually must either cancel by mail or phone. Some companies will let you cancel online. Call the company or go online to find the best method for your company.  To cancel by mail, print off the cancellation form online or ask the company to send it to you. To cancel online, look for the "cancel policy" button under your policy details. To cancel by phone, call the company's insurance department and ask for the cancellation department. You don't have to wait until your renewal date to cancel your policy. You can cancel any time during the year, so shop around if you'd like. If you're buying a new policy, you should have it in place before you cancel your old one. In some states, the company most notify the DMV when you cancel or get a new policy, so the state can fine you for the gap. Plus, if you get in an accident, you could be in serious trouble without insurance. In addition, sometimes rates will be higher if you a lapse between policies. In some states, you need proof of your new insurance policy before your old company will cancel the policy. In these states, if you don't have a new policy, you will need to show you have surrendered your plates. Call the DMV or go online to find out what your state requires. If you're not switching to a new insurance policy, some states require that you give your license plates back to the state before your policy can be cancelled. Check if your state requires it by calling the DMV or visiting the website for your state. You may think stopping payment is a good way to cancel your insurance. However, it's likely your credit score will take hit because of it. Plus, if you're switching companies, your new insurance company won't look favorably on this type of cancellation. It could raise your rates or be a reason for the new company to cancel your insurance.

Summary:
Contact your insurance company to find out the ways you can cancel. Cancel when it's best for you. Purchase a new policy before cancellation. Show proof of your new insurance. Surrender your license plates to the state. Don't just stop paying your insurance.