It is a common misconception that spark plugs create heat. Well, they do not. A heat range refers to how much heat a spark plug is capable of removing from the combustion chamber. Selecting a spark plug with the proper heat range will insure that the tip will maintain a temperature high enough to prevent fouling, yet be cool enough to prevent pre-ignition.
Spark plug gap and heat range should be paired with the power level of the car. A car with basic bolt ons would want to run a 2 step colder plug with a gap around .055″. A car with more than basic mods will want to run a plug about 3 steps colder than stock and a slightly smaller gap around .052-.050″. Turbo, N20, and highly modified cars (500 hp) will run the smallest gaps around .048 or possibly even smaller.