Beaver Basement Waterproof System
First check the gutters. I found that after replacing my gutters I no longer had water come into the main part of my basement. It was flowing over the old gutters and splashing over the sill into the basement.
Second check the grade, look for any low spots around where you think water is coming in. If you see any places that look washed down a bit, or you see gravel, more than likely thats where the water is getting in.
Third, take a peice of plastic and tape it down on the floor around where the water comes in and check it the next day for moisture, if you see moisture under the plastic, chances are the water is seeping in from underneath, and no matter what you do above the floor, you will always get water in until you resolve the reason for water under the slab.
If the third on is your problem you will need to hire a contractor to remove part of the slab around the perimeter of the foundation and put in a drainage system and sump pit.