A good question! it is not always obvious, especially if the misalignment is slight, but there are signs to look out for:
Uneven tyre wear on the fronts or the rears
If you can’t visibly see the wear, run your hands over the tyre and you
can soon feel where the rubber has worn excessively, on the inside or
outside edges. Warning – Be careful, in extreme cases of excessive wear fine wire may be protruding from the rubber.
The car pulls to the left and right
When driving along a straight flat road and you either need to
compensate through the steering to keep the car driving straight the car
drifts to the left or right under braking.
A crooked steering wheel
The steering wheel is not straight, even when driving straight.