Apart from cracks, look for:

• Doors and windows jamming: If your doors and windows are not opening and closing like they should and if the jamming against the frame is consistent in consecutive floors, it may be a sure sign of foundation damage.
• Roof damage: It may seem odd, but the top floors and the roof are among the first affected in case your foundation has moved. Go up to the attic, get between the roof and the floorboards, look closely for any signs of damage. The roof gets damaged because it is the furthest away from the foundation and even small changes down there will be amplified the higher up you go. If your home is brick built, look for step shaped cracks on the roof or in the walls that are in contact with the roof.
• A damaged foundation: The most obvious thing is to see length wisecracks on the foundation slabs. If they look like a log split along the grain, your foundation may be in trouble.

It is a distressing thing, but if you do see any signs, catching it early is the best way to reduce the amount of money you will eventually end up spending on it.