How do you design digital filters for process signals?

Digital filter design: FIR (Finite Impulse Response) - linear phase, always stable, higher order required. IIR (Infinite Impulse Response) - lower order for same cutoff, can be unstable, non-linear phase. Design process: specify requirements (passband, stopband, ripple), select filter type (Butterworth, Chebyshev, elliptic), determine order for required specifications, implement in DSP or microcontroller. Process applications: typically low-pass for noise reduction with cutoff based on signal dynamics. Consider: fixed-point vs floating-point implementation, computation time vs filter order, and group delay effects on control loops.