This is what I was told when I asked the same question during PPL training:
"Mostly, the only ice on the aircraft before flight is hoar frost, which can be removed with a large plastic scraper of the sort intended for cars. If the sun is shining, turning the aircraft so that the most icy parts face the sun helps.
If the aircraft was wet when the temp fell below zero (or if the frost melted and then frozen again), you may get patches of hard ice on the wings.
I carry a few large cans of car de-icer for this purpose. You can buy some stuff called Killfrost which is basically the same thing
(probably propanol) but comes in much larger containers and is much cheaper.
You need a garden-type spray to apply it. Keep de-icing fluid away from the fuel filler caps and static vents.
Don't mix de-icing fluid with water before use - it makes the de-icer less effective and may re-freeze on the cold aircraft again.
Finally, do remember that starting an engine in cold weather causes much more wear than in warm weather, also it puts a greater load on the battery. In cold weather I turn the prop by hand a couple of times before attempting to start."
Hope this helps...
[This message has been edited by Cahlibahn (edited 30 December 2000).]