During a heavy rain (without lightning of course), grab your umbrella and head outside. Take a walk around your home and look at your roof and property. This is the perfect time to see how your roof, gutters, downspouts and grading around your home are performing. The ground around your home should slope away from all sides. Your downspouts, surface gutters and drains should all be working together to direct water away from the foundation.
In most cases, problems with moisture in basements and crawlspaces are caused by poor site drainage. The ground should slope away from window wells, outside basement stairs, and other means of egress. The bottom of each of these areas should be sloped to a drain. Each drain should have piping that connects it to a storm water drainage system (if there is one) or that drains to either a discharge at a lower grade or into a sump pit that collects and discharges the water away from the home.
If your home is situated on a hillside, it's more difficult to slope the ground away from all sides. On the high-ground side of the home, the slope of the ground towards the home could be interrupted by surface drainage that collects and disposes of rainwater runoff. Swales are a way to direct surface water away from the foundation. Two different types of surface drainage systems could be used: an open system, consisting of a swale ( or ditch) , sometimes with a culvert at it's end to collect and channel water away; and a closed system, consisting of gutters with catch basins.
Planters & Downspouts.
If your home has any planting beds near the foundation make sure they are not up against the homes exterior wall. Planting beds are built in a way that traps water.
Puddles are usually not a good sign. The ground surface beneath decks, porches and other parts of your home that are supported by posts should also be checked. You should not have any low areas, but should be sloped in a way that water will not collect or pond. Settled backfill allows for the water to collect and slowly come in through and penetrate into the basement.
Your downspouts may need to be adjusted. Water from the roof reaches the ground through gutters and downspouts or from directly off the roof edges. Since downspouts create a lot of water runoff it is important where they discharge. Downspouts should not discharge directly on or over a walkway, driveway or stairs. The force of water leaving a downspout is sometimes great enough to damage the adjacent ground, so some protection at grade might be needed such as splash block or a paved drainage chute, is needed.
If a sump pump is installed at the home, it should not recycle. When a sump pump is used to keep a homes interior dry, the discharge should drain away from the home and should not add to the subsurface water condition that the sump pump is meant to control.