First, find where the water comes from
Water in the basement is a symptom, not a diagnosis. The fix depends on where it gets in. Look at where the puddle starts and when it shows up.
At the base of the wall
Water where the wall meets the floor is the most common leak. Water in the soil pushes in at that joint.
From a crack
A wet line down a wall means the crack goes all the way through.
Up through the floor drain
Dirty water coming up the drain in a big storm is usually a sewer backup, not the foundation.
Through the floor
Water rising through floor cracks points to water under the slab.
At a window
A window well that fills up can pour water in.
Everywhere at once, only in summer
Damp walls in humid weather can be condensation.
In one spot, any time
Check the water heater, washer and pipes before blaming the walls.