Clogged overflowing gutters can lead to rotten fascia boards and even cause damage to the foundation. Clean them during dry weather starting at the downspout and working back. Wear gloves and use a gardening trowel or a scoop made from a plastic container.
Rather than throwing the leaves and debris away, put them on your compost pile. After the gutters are clean, use a garden hose to wash out the inside, and check to be sure the downspouts are flowing freely.
Of course, some tools can protect your gutters year-round. Like GutterBrush Leaf Guard: