[Christ]

Check for the pillow mounts for McP strut systems: remove the lower attachment point on the strut, leaving it attached to the body/chassis of the car.

begin wiggling. immediately, the side to side movement should feel arrested, any loose feeling to the motion is cause to replace the bushing/mount.

Recommended replacement interval is something like 60k for newer ones. You can get away without replacing them in most cases, but a visual inspection is necessary. My wife's GP has a nice plate on the top of the strut mount that actually stops the strut from contacting the hood. It also prevents the strut from pushing through the hood in the event that the rubber bushing fails.

A pretty standard upgrade that will also help to stiffen your ride a little bit (attenuation of lateral movement) is to use ball mounts instead of pillow mounts. These are essentially solid, but employ a heim joint's "eye" as the location where the strut's piston actually is mounted.