How do I know if my gutters are clogged?

How do I know my gutters are clogged and do I need to clean them?

soil or mulch washed out around the foundation of the house
• discoloration of the gutter
• In the event the gutter is over
  the driveway or a walkway, you should look for discoloration on the area under the gutter.
• water running down the side of your home
• water in your basement

Typically you should check on the gutters 4 times per year.  You will likely need to clean them out 1-2 times per year.
You don't know what may clog up your downspouts- tennis balls, birds' nests, a stick, roofing sediment. This is all in addition to the seasonal debris- seeds in the spring, leaves in the fall.