Correct TVS diodes location on the PCB provides optimal protection from surge, an application note from ON Semiconductors. Link here (PDF)
Transient Voltage Suppressors (TVS) avalanche diodes and diode arrays can be used to protect sensitive electronic components from the surge pulses that arise from ESD and EMI. The small size, fast response time, low clamping voltage and low cost of TVS diodes provides for an effective solution to prevent surge problems. Avalanche TVS diodes and diode arrays are relatively simple devices to use to suppress surge voltages. Only a few PCB design rules must be followed to optimize the ESD and EMI immunity level of the protection circuits.