There are circuit examples for overvoltage protection of analog inputs, but usually this is not referred to as "surge protection".
In many cases, it is sufficient to connect diodes in reverse direction from the input(s) to the VCC+ and VCC- rail. This will limit the input voltage(s) to the supply voltage(s) level, plus the forward voltage of the diodes (usually less than 1V). You should consider the leakage current of the diodes, if necessary, use low-leakage diodes such as the 1N457, otherwise, in most cases the 1N4148 are sufficient.
To protect the inputs of an operational amplifier (which should be at almost identical levels when the circuit is operating properly) you can connect two diodes in anti-parallel across the inputs. This will limit the differential voltage across the op amp inputs to the forward voltage of the diodes.
Another method is using zener diodes from the input(s) to GND. The nominal voltage of the zener diodes should be somewhat outside the normal voltage levels, since zener diodes increase their current significantly close to the zener voltage. Again, you should consider the leakage current in the "non conductive" area.
All this is not really "surge protection" since the circuits described can handle small currents only, the diodes will burn when overloaded and you never know what they will do then, in most cases they are interrupted. To handle large surge currents, you may use transzorber diodes, they can handle very high surge currents but have leakage currents significantly higher than zener diodes. Also, if you use diodes connected to the supply rails (as described above), the surge current will flow into the power supply.
