Use an initial tolerance of 10 in the Optimization Properties dialog box when you know very little about the optimal parameter values; otherwise, the algorithm will take a very long time to search a short distance in parameter space.
Once optimal values are found, the parameterUnknowns can be reinitialized with the new optimal values and the optimization can be rerun with a lower tolerance.
Though the algorithm tries to avoid local minima, to verify that the values found are optimal, run the optimizer with different initial values supplied to the parameterUnknowns.