Look for bowing of wall itself in an inward direction by using the longest level you have or a straight piece of lumber. Placing the level in a vertical position and slowly moving it along the wall will indicate by being able to "rock" the level, that the wall is bowed. You should be able to keep the level firmly against the wall.
If you find a bowed condition, it could indicate an outside pressure is being placed against the wall. This may be caused by by several things. Many types of soils when wet will place extra side stress on the walls.
Shifting soils on the exterior may also place extra stress against the walls causing them to bow and crack. Look for exterior changes to the area around the home. Look for things such as collapsed retaining walls, sliding embankments, excess water runoff, broken gutters and anything that did not exist in the past.
Foundation drainage is significantly important. Most homeowners don't understand that water in or around the foundation is the main cause of foundation failure. Poor drainage around the foundation can even threaten its structural integrity. If runoff from rain and snow isn’t channeled far enough away from home, it could saturate the soil and destabilize the foundation. It’s both easier and cheaper to install a good drainage system than it is to fix a damaged foundation.
Is the exterior grading still allowing water to run away from the foundation wall? All of these things can cause excess water to gather outside the foundation wall, soaking the ground and then causing ground shift. Look for a blocked footing drain outlet pipes. If this pipe is plugged water cannot escape from around the foundation perimeter and thereby cause a foundation leak.
If the bow in the wall is minor and cracking is at a minimum, you may be able to repair the wall yourself. Using a four inch hand grinder with a masonry blade cut out small portions of the cracked masonry joints and re-point or patch them with new mortar. Do small areas at a time so as not to compromise the integrity of the overall wall. But to save yourself time and effort you can get the retaining walls services to get the job done for you in a much efficient way.
Application of a a sealer such as Dri-Lock on the wall will also help to seal out ground water. However if there is a high concentration of water from any of the reasons I listed above, they must be corrected first. Make sure when applying the sealer that you paint it down and out onto the floor about two inches or so to provide a seal at the wall to floor joint.
Concrete foundation walls are a bit easier to patch. Again if the crack appears to be simple shrinkage of the concrete, using the same four inch grinder, open the crack to the thickness of the blade and approximately one inch deep.
Go no deeper as the reinforcing bar is generally held two inches from the face of the concrete wall and you do not want to damage it. There are lots of caulk gun type sealants available today that are made just for concrete. Make sure you penetrate all the way into the crack when applying the sealant and allow for air drying if you are going to cover the sealant with new wall finishes.
If the exterior side of the foundation wall, either concrete or CMU units, was properly patched and waterproofed before back filling, these simple repairs should leave a nice dry basement.
If the walls show either severe bowing or large cracks there may be a loss of structural stability. Have a structural engineer or architect examine the walls to determine if they need to be replaced or what other repairs may be needed. Shoring and other work may be required so do not start removing the walls before consulting a professional first.