If you haven't done so already, check the AFM for your particular aircraft on what they state constitutes "icing conditions".
For example, Beechcraft, in the B200, state that it's visible moisture below +5 Celsius.
Reason why it isn't zero degrees is, very simply, it gets colder in places inside the engine intake and ice can form. Sometimes this sheds and can damage the first stage compressor blades.
Also look for your minimum icing speed. Staying above this helps to keep ice from accumulating on areas of the airframe that don't have protection.
If you are flying an aircraft equipped with pneumatic boots, let ice accumulate on the leading edges before popping the boots; if you pop too early it may not break off cleanly and the next layer of accumulation will be harder to remove.
When ice sheds off the prop blades and hits the fuselage it will probably scare the crap out of you the first time you hear it.
Make sure you know the difference between "de-icing" and "anti-icing" gear on your aircraft.
My icing experience is very limited so can't give much more advice sorry. It can easily and quickly kill you, so treat it with the respect that it deserves.