Although a rather meaningless number because of a lack of standard in its definition, the treadwear defines the wear rate of the tire.  Since usually a tire with a high friction coefficient wears faster, it is the closest thing to identify the friction coefficient:  The lower the treadwear, the higher the friction coefficient.

Traction indicates the tire's ability to stop on WET pavement.  This is not related to the dry friction coefficient.  For example, DOT legal racing tires with limited tread depth fare poorly in this rating.  For a daily driver (which will be driven in the rain), you shouldn't use anything below an “A” rating; For a true performance vehicle, nothing else than an “AA” rating should be considered.

Temperature grades are an indication of a tire's resistance to heat. Sustained high temperature (for example, driving long distances in hot weather), can cause a tire to deteriorate, leading to blowouts and tread separation.   Again, for a high performance daily driver, anything below an “A” rating is unacceptable.

If you get a high performance tire with low treadwear and high temperature grade, the speed rating will be pretty much a given.  Still, just make sure it is high enough for your use.

An overlook rating is the load index.  Tire friction coefficient tends to decrease as the load increases.  It gets worst as the tire reaches its load capacity.  To get a more uniform (and higher) friction coefficient from a given tire compound and construction (i.e. comparing different sizes from the same tire make and model), use the size that gives the highest load index.  Usually, the greater the tire diameter and the larger the tire width, the greater the load index.

The date the tire was manufactured is indicated at the end of the tire identification number (following the letters “DOT”).  It is composed of four digits: the first two representing the week and the last two the year.  For example, “5107” means the tire was manufactured in the 51st week of 2007.  Tires with three-digit dates were manufactured before 2000 (single-digit year).  It is possible that the date is indicated on one sidewall only.

The structural integrity of a tire can degrade over an extended period of time. When that occurs, tires are more prone to catastrophic failure, which could, at best, cause an inconvenience, or, at worst, lead to a crash. The degradation of a tire occurs over time, mostly the result of a chemical reaction within the rubber components. That aging process can be accelerated by heat and sunlight.  The effects of aging may not be visibly detectable.  Usually tires should be used within 6 years, no more than 10 years for sure.