It is increasingly difficult to guarantee the first silicon success for complex integrated circuit (IC) designs. Post-silicon validation has thus become an essential step in the IC design flow. Tracing internal signals during circuit's normal operation, being able to provide real-time visibility to the circuit under debug (CUD), is one of the most effective silicon debug techniques and has gained wide acceptance in industrial designs. Trace-based debug solution, however, involves non-trivial design for debug overhead. How to conduct signal tracing effectively for bug elimination is therefore a challenging task for IC designers. In this paper, we provide in-depth discussion for trace-based debug strategy and review recent advancements in this important area.