1) Know the plan you select. Every Insurance carrier has different Benefits, You need to read and study your policy, know what it covers and does not cover.Be sure that your agent gives you a summary plan description of the plan your purchased, and when you get your policy in the mail, be sure you read every page to understand what it covers and does not cover, You can also call the company who issued the policy and they can go over the benefits with you.
Consumer reports has a good comparison chart at www.consumerreports.org/health.

2)  Know the Details of each benefit before you go in the hospital.
Does it cover the medical equipment, what does it pay for in room benefit, some people get private rooms, and the contract only pays for semi private, and are stuck with a bill when this could have been avoided. Know the details of your polilcy before you need to use it.

3) What can you afford?  If you have the money in the bank, take the highest deductible possible and self insure your risk, the lower the deductible the higher the premiums are, know what you can afford. Look at HSA plans and Consumer driven plans, these plans will save you money if you are healthy, if you have a chronic illness and use your insurance a lot, you should look at lower deductibles and maximum out of pocket.