The carpets down in the foot wells, along the rocker panels, even take up the rocker cover to see if water got inside it. Also along the floor behind the rear seat. Any low point in the floor is where water will collect.

 

 

Year make and model? Heater core leak? AC condensation leak?

 

 

Do you have a sunroof? If you do are the drain lines clear of dirt and debris? Also check under the dash where the A/C condenser is and be sure the drain there is open.

 

Check your sunroof tracks and make sure they are draining.....assuming you have a sunroof!

 

 

Passenger side behind the glove box is where most vehicles have the condenser and fan for the a/c. Sometimes the drain will partially plug up and water (condensate) will collect in the bottom of the box spilling out if you make a hard turn. run your A/C a bit on a humid day and look for it to drain onto the ground near the front passenger wheel well. Look up underneath and find the outlet of the drain tube. If you take a stiff wire and run it up to clear the drain and get a deluge you found your problem.