The federal government's Uniform Tire Quality Grading System provides consumers with some comparative data on tire performance. You'll find the ratings on the tire sidewalls. Look for either an A or B temperature rating.
Tires can harden and crack with age, so steer clear of old stock.
Every tire carries a serial number on the sidewall. The last three digits are a date code indicating the week and year the tire was made. Check tire pressure monthly. If the tire pressure is low, the tires will wear more rapidly and fuel economy may suffer a bit. If the pressure is low, heat can build in the tire that may cause it to fail.