When it comes to shopping online, few purchase decisions will carry the magnitude of the one you'll make if you buy health insurance under Obamacare. Open enrollment starts in just over a month, on Oct. 1, for policies that would take effect on Jan. 1, 2014. So, if you need health insurance, it's time to start familiarizing yourself with the Affordable Care Act. Shopping for health insurance will become considerably different than it is today for most Americans, allowing consumers to shop through an online health insurance marketplace. There, you'll be able to compare prices as well as decide how big a deductible you'd like and how much of a co-pay you're willing to take on. Buying health insurance isn't as simple as choosing between Nike and Adidas. And you have to live with the decision you make until the next open enrollment period. 3 basic levels Making the choice is going to involve some thought, because a lot of options are going to be on the table. In Massachusetts, which already has a health insurance marketplace and serves as something of a model for other states and the federal government, insurance is offered in tiers -- gold, silver and bronze -- to help consumers sort out the choices. Bronze is the least expensive, but has larger co-pays and bigger deductibles, than the more costly gold plan. There are also levels for each tier, giving consumers additional options to, say, shave off some of the monthly premium cost by accepting higher co-pays. Prices will be shown for each insurer at each level. So, picking through the plans involves some thought and decision-making based on how much you're willing to pay on a monthly basis balanced with how much risk you're willing to take in case of a serious illness or injury or the amount extra you would have to pay for frequent doctor visits. Differences among companies Once you've sorted through the issue of price versus deductible and co-pay, the next step is comparing insurers. As similar as the plans might be, cost is unlikely to be the only difference between companies. This is an area where it is vital for consumers to do some homework. Why? Not every provider accepts every insurance plan. Be sure your doctor, if you'd like to keep that doctor, accepts the plan you're considering. And if you don't care whether you're doctor is on any particular plan, still check the provider directory of a plan you're considering to see what doctors are available to you. Some plans could have considerably thinner participation in certain areas, and that's something you don't want to find out when you actually need to use your insurance. The carriers who offer the fewest options for coverage tend to also cost the least, so don't use price as the sole determining factor. For those who have health insurance through an employer, these choices won't be relevant. But for those who are self-employed have been gambling by not having health insurance, or couldn't get a policy because of a pre-existing condition, shopping in the new marketplace will be an opportunity. Just be sure to take the time to compare, and understand the decisions you're making. .