If you do find that you have an ice dam, do not go up on your roof. Any large icicles that are above doorways should be knocked down with a broomstick to avoid any injury. As for the dams, although it may seem like the best solution is to just break apart the ice dams to allow water to flow, it is very dangerous. Using a ladder in snowy conditions is not safe, especially when wielding a sharp or heavy object to break ice with. If you have a dam, the best thing you can do is to hire a professional to clear it up for you. However, with a little planning, ice dams can be easily avoided.
The first thing you should do is make sure that your attic is properly insulated. Insulation type and thickness depends on your location. Thicker insulation is needed for homes in colder climates, and less for homes in warmer weather. Make sure there is enough space between the roof and the insulation to allow air to circulate. Check for holes or cracks in the attic floor and fill them with spray foam for a tight seal. You will find that this is the best long-term solution to the ice dam problem, and will result in energy savings in both the winter and summer months. There are also seasonal solutions to ice dam prevention. Before there is heavy snowfall, install heat wire above the eaves to prevent any ice accumulation. You can also avoid ice dams by using a snow rake to remove snow from the roof before it starts to melt.