I came across a product that claims to prevent tire punctures. It's some kind of liquid sealant that you fill your tires with. Should I give it a try?
How often do you encounter a puncture? Or more pertinently, a puncture you cannot rectify painlessly?

 In big countries where punctures to more than one tire could be a major hassle, such sealants may be warranted.  Also, liquid in tires could affect their dynamics, especially at higher speeds.
If you want, you could fill your tires with nitrogen, an inert gas that does not leak through microscopic pores of rubber as easily as air. Interestingly, air itself is made up mainly of nitrogen.
Formula One racers fill their tires with pure nitrogen, as the gas does not expand as much with heat. You can do it too at some upscale tire shops.