First, you should read this important information brochure from EPA called Filtration Facts (a downloadable PDF file) to get familiar with different options for different types of contaminants.
NSF, a highly regarded independent product certifying organization, offers these valuable tips in filter selection and the terminology used in the type of filters.
The following chart shows the type of water filtration methods used for various contaminants based on their size.
As your body can absorb toxins such as Volatile Organic Chemicals (VOCs) in showers and bathtubs, the best option, if you can afford the cost, is a whole house water filtration system such as a reverse osmosis product, which can cost anywhere from $500 to several thousand to install and a few hundred dollars a year to maintain depending on the capacity.
At a minimum you will need a counter top drip filter carafe with activated charcoal for removing VOCs in your drinking water. These are inexpensive, costing under $100.
Consumer Reports recently reviewed a few of the major consumer filtering brands. You need a subscription to Consumer Reports to view the details.
Environmental Working Group (EWG), a non-profit organization offers this well researched guide for consumers to help them select the right filters for their needs.
NSF has organized its certified filtering products by manufacturer, by brand, and by the type of contaminant you want to filter out. It is a comprehensive database for you to narrow down your choices to one or two to meet your filtering needs at home. It is a free service.
But be warned that most of the certified, commercially-sold filtering products do not necessarily filter out unregulated contaminants. Pristinet plans to remedy this shortcoming by gradually expanding the list of certified products to include those that filter unregulated contaminants.