If the glacier isn't snowless (aper) you can probe for spaces under the surface which should be noticed by less resistance in the snow/Firn. Still it is preferable to avoid going in regions where one would expect crevasses. This isn't easy like it is tough to know how the weather is going to evolve in the mountains. But still we could try to use some theory to spot possibly dangerous areas.
Glaciers are moving, they are literally flowing. Crevasse are a result when this flow is getting influenced/restricted by e.g. elevation through rocks under the ice, different slopes or merging of different glacier flows. So it's all about the different flow velocity of the ice. This is similar to fluids. Being in your dinghy on a rock-loaded river, even when you can't see those rocks they will cause you some issues. Glacier ice is more or less solid and can only deform to a certain point, then it breaks and we are getting those inhospitable yet beautiful - this summer I was let off into one, it was impressive - crevasses.
There are mainly four types of crevasses:
A crevasse oriented more or less perpendicular to the long axis of a glacier. Transverse crevasses typically open on a valley glacier when the terrain becomes steeper, such as above an icefall.
A crevasse oriented more or less parallel to the long axis of a glacier. Longitudinal crevasses typically open on a valley glacier when the glacier becomes wider.
Series of crevasses oriented at an angle to the glacier margin. These form as a result of rotational strain within the ice along the glacier's edge.
They form due to the velocity difference (slower edge area compared to the faster main glacier) lateral to the moving direction of the glacier.
A bergschrund (from the German for mountain cleft) is a crevasse that forms where a moving glacier ice separates from the stagnant ice or firn above