If you are buying bottled water make sure it has been filtered with reverse osmosis. While generally regarded as too expensive for personal use but is appropriate for bottling water plants and it means that they have filtered out fluoride from water.
In areas where fluorosis is common you need to buy an activated alumina
de-fluoridation filter. This will require frequent filter replacement but is the best way to protect your family. Another option is distillation filtration that is also a suitable option to filter out fluoride from water.
Be attentive to the attributes of the filter not every filter removes fluoride and paying attention when buying saves you from spending money on a filter that won't really help you.
Some of the most popular models do not cater to fluoride removal and so need you to do research. Boiling water with fluoride does not remove the fluoride but only succeeds in concentrating it. Freezing the water also has no effect on the concentration of the fluoride content in the water. Make sure you also avoid ingesting fluoride from other sources like toothpaste, canned foods, some bottled beverages and long term use of medication.