The most effective way to determine if a planet experiences plate tectonics is to look for the telltale signs found on Earth. Several of the features that could be searched for are:
Mid-ocean ridges
Rings of volcanism
Deep linear trenches in the oceans.
A satellite topography scan of the planet would reveal the shapes of the mountain ranges and valleys on the planet. If these tend to be lineal and covering significant parts of the planet, then plate tectonics likely occur.
The correct answer to this open question is the following.
The best indication that the planet may have plate tectonics could be, in the first place, if the planet has a magnetic grid. We can check if the surface of the planet is stable and has mountain ranges, valleys, and faults. If that is the case, then the planet has telluric movements and movement of the plates.
