Pinch flats are prevented by running the widest tire you can fit at the correct tire pressure. Make sure you check you pressure every couple days.
Punctures from the rim are prevented by cleaning burrs off the inside of the rim and using a good cloth rim tape.
Punctures from road debris are best prevented by using a good puncture resistant tire. On lightweight or inexpensive tires I get several flats a month, on good kevlar belted tires I get less than on a year. The Marathon Plus tire is probably the beefiest tire available and come in a variety of sizes. The Marathon Slick, Armadillo, and Gatorskin are faster tire that are still tough on punctures. I perfer a good tire over a tire liner but others perfer the opposite.
Make sure you take care of the first two items then get yourself a good tire.
Craig