Start every winter season with completely cleared gutters. Ice is less likely to build up and cause dams if there is nothing in your gutters when the temperature drops.
Check your downspouts for blockages. Clear any debris from the downspouts, and melting water from the gutter ice will begin to run off immediately.
Remove excess snow with a roof rake by pulling the snow downward in the direction the roof slopes. Do not pull the snow across the roof because you run the risk of breaking off shingles. (Roof rakes can be purchased at most hardware stores.)
Use a chisel, large screwdriver or the back of a hammer to chip away at a small portion of the gutter ice. Don't start chipping until the snow has been swept off the roof. You only need to chip enough ice to create an area through which water can flow. Chip gently; your gutter is already under an enormous strain.
Hose down the gutter with hot water. This step is optional. As long as the snow is cleared off the roof, gutter ice will melt quickly as the temperature rises. If you feel you can't wait for this, hose down the gutter to melt the ice. Only use a hose if it has a spray nozzle and you can produce hot water. Also, the temperature must be warm enough for the water to not freeze on contact with the ice.
Consider the installation of gutter guards and aluminum heating panels or wire mesh heating guards.