With the CMOS technology reaching its limits, the design of cyber physical systems is becoming more and more complex. Securing the performance in terms of resolution, speed or flexibility would require a more intensive use of digital assistance to compensate for the increased challenges on the RF and analog parts.This tutorial will provide an overall overview of how to design, size and implement a digital assistance to compensate for a given non-ideality. All the main steps will be covered from the modeling approach to the implementation in fixed point. The major caveats for each topic will be discussed in order to materialize the limits of the presented methods and models. Concrete examples as well as live experimental demos will be presented for several applications such as Digital Pre-Distortion for Power Amplifiers, Digital correction of Stacked and Time Interleaved ADCs and Dynamic Element Matching Techniques for Digital to Analog Converters.