There are many signs that your foundation has damage but you may not notice or be aware that they are warning signs there is a problem.
Cracks in brickwork - these come in all shapes and sizes but depending on the specific problem you have occurring is a definite sign of foundation issues and a contributor to cracked drywall.
Cracks in corners - If you have vinyl siding or other siding material often times the shifting of your foundation can cause separation issues and widening gaps between pieces of siding.
Cracks in the floor - Whether you have ceramic tiles, concrete slab floors, etc. cracks in the floor are a sure sign of settling or shifting of your foundation. These problems only worsen over time if not stopped.
Cracks in drywall - these are the most commonly noticed issues by homeowners. One second your drywall looks great the next you notice a hairline crack starting that gets bigger and bigger over months or years. This is a sign you have foundation problems that need to be resolved. These problems are causing the foundation to shift and your walls to move to result in cracks.
Gaps in door frames or windows - ever notice a window or door suddenly becoming really tight? How about large gaps forming around them? These are both signs that your walls have moved and likely a result of foundation issues.
Leaning chimney - If you have a chimney that seems to be leaning away from your home there is a good chance the foundation below has sunk resulting in the lean.