A good way to immunize your home against ice dams is to reduce the attic temperature. First, make the ceilings of the house air tight so no warm, moist air can flow from the house into the attic space. One way is to install additional insulation on the attic floor or have more insulation blown in.
Install weather stripping and/or insulation on attic stairways or hatchways, and on attic floor-mounted louvers for whole house ventilation fans. Be careful if there are any exposed recessed light fixtures or vent fans poking through the attic floor. Some of these are not designed to be covered with insulation and information from manufacturers is available whether they can be covered or not.
Do not pack insulation deep in the corner where the roof meets the attic floor. This causes the roof area near the eaves to be colder than the rest of the roof, setting up a possible ice dam formation. If you have blown-in insulation, there are Styrofoam dams, that can be installed between the floor joists to hold the insulation back from the inside of the roof.
The same holds true for soffit vents in the exterior overhang of a house. If you have them in the overhang, do not let insulation block the air-flow from the soffit to the ridge vent of your roof.