how do you know if a circuit is common gate drain source if...?

Combinations of devices are known by different classifications such as cascode, differential pair, current mirror, totem pole, complementary, bridge etc., mostly according to function, configuration, sometimes by the original designer, and so on. You need to show the circuit. With mosfets the individual transistors are nearly always used in some variation of common source.

The source may not be grounded, as it can be connected to the drain or source of other transistors and vary over the power supply range. Common source means that the gate and drain circuits share the source s the connection common to both circuits. A P-channel will be inverted in a typical circuit with N-channel devices (positive supply), with its source nearer to the positive rail than its gate voltage range. Note that current in the channel can be in either direction, apart from the substrate diode.