1. A rule-based method for controlling sootblowing at power plants comprising: providing a control computer coupled to a sootblowing control system that controls a plurality of sootblowers; providing a plurality of sootblowing rules stored in said control computer; providing a plurality of physical parameter inputs to the control computer including temperature, pressure and flow values related to various sootblowers; providing a set of computer instructions stored in memory in the control computer executable by the control computer to evaluate a fuzzy function of the physical parameter inputs, the fuzzy function being configured to evaluate tradeoffs in time overdue for activating a particular sootblower and importance of the particular sootblower to determine a ranking of all sootblowers controlled by the control computer and a time window for each sootblower to run, said fuzzy function also adapted to take into consideration effects on the physical parameters relating to other sootblowers when the particular sootblower is activated; wherein, said control computer operates said sootblowers according to said rules and said fuzzy function.