  We use symmetry considerations to investigate how damped modes affect pattern
selection in multi-frequency forced Faraday waves. We classify and tabulate the
most important damped modes and determine how the corresponding resonant triad
interactions depend on the forcing parameters. The relative phase of the
forcing terms may be used to enhance or suppress the nonlinear interactions. We
compare our predictions with numerical results and discuss their implications
for recent experiments. Our results suggest how to design multi-frequency
forcing functions that favor chosen patterns in the lab.
