There are quite a few products you can use to predict icing. Nothing is more important than to understand the weather phenomena most likely to cause icing either on the ground or the air. Most jets consider a temperature range of +10deg C to -40deg C with visible moisture as icing conditions and this is a good place to start. Take a look at a winds aloft and determine if the temperature is in that range. I would then take a look at the area forecast briefing to see where clouds are or other visible moisture. Weather specialists will also issue Airmet Zulu for icing conditions.

(The pictures are automatically updated as new weather is released)

http://www.aviationweather.noaa.gov has some really good graphics for icing.
Icing Sigmets

Maximum Icing Severity

Anywhere you see "SLD" depicted; I would stay away or get out of icing conditions as quickly as possible. "SLD" stands for super-cooled large droplets. To say the least, they are large liquid drops of water whose temperature is 3-5deg below freezing. They freeze fairly quickly on the airframe but tend to move aft past the deicing boots or anti-ice systems before completely turning to ice. Once that happens, there is no way to get the ice off of the airframe.

One last thought. If conditions are conducive to icing as evaluated from a reasonably average pilot and you decide to go flying through it without an airplane that is certified for known icing; the FAA won't be too happy and the insurance won't cover the accident that might transpire from such a decision.